Marxism bears the marks of Hegel’s influence, and it’s foolish to attempt to rewrite that history so that he doesn’t blemish it, or to neglect this fact as if it were void of insights.
The first thing to come to terms with is that Hegel mattered to Marx. The idea that Marx is a “slayer of Hegel” is a gross distorsion of the relationship between the two men:
My relationship with Hegel is very simple. I am a disciple of Hegel, and the presumptuous chattering of the epigones who think they have buried this great thinker appear frankly ridiculous to me. 
Lenin is no less emphatic:
It is impossible completely to understand Marx’s Capital, and especially its first chapter, without having thoroughly studied and understood the whole of Hegel’s Logic. Consequently, half a century later none of the Marxists understood Marx!! 
More important than tracking declarations of intellectual debt, however, is identifying how this debt manifests in fact. Consider the way Hegel’s thought reverberates in the pronouncements of major figures in Communist history:
|Marx||It is only in the markets of the world that money acquires to the full extent the character of the commodity whose bodily form is also the immediate social incarnation of human labour in the abstract. Its real mode of existence in this sphere adequately corresponds to its ideal concept. ||The completed idea of the will is found when the conception has realized itself fully, and in such a manner that the embodiment of the conception is nothing but the development of the conception itself. |
|Engels||Freedom does not consist in any dreamt-of independence from natural laws, but in the knowledge of these laws, and in the possibility this gives of systematically making them work towards definite ends. ||In that individuals belong to the ethical and social fabric they have a right to determine themselves subjectively and freely. Assurance of their freedom has its truth in the objectivity of ethical observance, in which they realize their own peculiar being and inner universality.  |
|Lenin||The two basic conceptions of development or evolution are: development as a cycle of increase and decrease, and development as a unity of opposites. […] The first conception is lifeless, pale and dry. The second is living. ||Something is therefore alive only in so far as it contains contradiction within it, and moreover is this power to hold and endure the contradiction within it. |
|Stalin||Every new generation encounters definite conditions already existing, ready-made, when that generation was born. And great people are worth anything at all only to the extent that they are able correctly to understand these conditions, to understand how to change them. ||Every kind of falsehood and truth is present in public opinion, but it is the prerogative of the great man to discover the truth within it. He who expresses the will of his age, tells it what its will is, and accomplishes this will, is the great man of the age. |
|Mao||It is precisely in the particularity of contradiction that the universality of contradiction resides. ||The non-being of the finite is the being of the absolute. |
In short, Hegel had important things to say.
In the same way that we find Hegel’s thought alive downstream of his writing, so with ancient thought in Hegel:
Something moves, not because at one moment it is here and at another there, but because at one and the same moment it is here and not here, because in this ‘here’, it at once is and is not. The ancient dialecticians must be granted the contradictions that they pointed out in motion; but it does not follow that therefore there is no motion, but on the contrary, that motion is existent contradiction itself. 
Far from being exclusively backwards-looking, or absent-mindedly musing about the meaning of meaning, Hegel more than left the door wide open to the application of his thought to modern political economy:
Hegel proposes that the market economy is a “monstrous system” that needs to be “tamed like a wild beast,” as he puts it in the early Jena years. Lisa Herzog has convincingly shown that this remains Hegel’s position in his Philosophy of Right, where, while drawing on Smith’s account of the price mechanism or “invisible hand,” he remains critical of said mechanism. 
In all of these samples Hegel’s thought is characterized by (1) “seeing the positive in the negative” (e.g. Yin and Yang in Daoism, in rejection of simplistic “inherent good vs. inherent evil” in Christianity), while at the same time (2) rejecting the cynicism inherent to “cyclical” thinking proper to both pre-moderns and post-moderns:
Education always begins with fault-finding, but when full and complete sees in everything the positive. In the case of religion one may say off-hand that this or that is superstition, but it is infinitely harder to conceive of the truth involved in it. 
Hegel unsettles liberals insofar as he threatens their weak claim on the notion of progress, which in their hands is reduced to the mere individualistic “self-realization” of the bourgeois subject.
Hegel also said a lot of backwards nonsense. His attitude towards war seems like mere poetic dressing over the “it makes boys into men” sentiment flaunted by every stripe of bloodthirsty reactionary today:
Just as the movement of the ocean prevents the corruption which would be the result of perpetual calm, so by war people escape the corruption which would be occasioned by a continuous or eternal peace. 
We can see, however, how such a belief would arise as a rather natural consequence of attempting to “see the good in the bad.” It illustrates clearly the problems with this approach: if you rush ahead to seek justifications — “what is rational is real; and what is real is rational”  — you may stop short of truly grasping the real depths of the depravity of what you are defending, you may short-circuit your process of empirical learning in favour of callously marveling at the unfolding logic of reality.
This same vice leads us to what is most excreable in Hegel today: his undeniable racism, his misogyny. As just one disgusting example out of many, he defends the practice of slavery as follows:
Negroes are enslaved by Europeans and sold to America. Bad as this may be, their lot in their own land is even worse, since there a slavery quite as absolute exists; for it is the essential principle of slavery, that man has not yet attained a consciousness of his freedom, and consequently sinks down to a mere Thing — an object of no value. Among the Negroes moral sentiments are quite weak, or more strictly speaking, non-existent. 
The best we can say for Hegel’s prejudices is not that they follow from careless reliance on the “state of the art” knowledge he was fed — “garbage in, garbage out” is, after all, the classic excuse for all racists. The best is precisely that which is not common to these other racists: that fact that Hegel’s prejudice is (however insufficiently) aware of its own contingency, the fact that his philosophy carries within it an implicit rejection of chatter about the “essential traits” of this or that human group, the fact that he asserted that race “science” merely attempts to justify prevailing prejudices after the fact:
To try to raise physiognomy and above all cranioscopy (phrenology) to the rank of sciences, was therefore one of the vainest fancies, still vainer than a signatura rerum, which supposed the shape of a plant to afford indication of its medicinal virtue. 
The relevance of Hegel in philosophy is comparable to the political-historical relevance of the Soviet Union, particularly that of Stalin. Bourgeois historiography has devoted inhuman amounts of effort to ensure that nobody dares speak a kind word about that political experiment, and this has had the result of arresting the political development of human society world-wide for decades, with “activists” futilely trying to find “non-authoritarian” solutions that bear no resemblance to the “tragedy” of the Soviet Union. There’s a similar conspiracy of silence or ridicule surrounding Hegel in Anglo-Academic philosophy circles, despite the fact that any serious study of the history of the evolution of Western philosophical thought generally leads from Spinoza to Kant to Hegel. Hegel, of course, leads to Marx and Engels. To avoid this natural outcome newcomers are presented with canned alternatives: either the “irrationalist” track of Nietzsche and Heidegger and Derrida and Foucault, or the impossibly dweeby “dispassionate intellectualism” of clinical analyticals. The rest, as they say, is history.
Hegel is a lot more readable than he’s made out to be, but the point here is not to urge a rediscovery of his texts. Rather, what’s truly important is understanding the polemic around him, and around all thought like his own. As Lenin put it:
No natural science and no materialism can hold its own in the struggle against the onslaught of bourgeois ideas and the restoration of the bourgeois world outlook unless it stands on solid philosophical ground. 
This bourgeois world outlook was, in fact, restored. Hegelian dialectics is one of the many tools with which we will tear it down once again.
 See also the popular C. J. Arthur paraphrase, often attributed to Hegel himself: “But if men realize that their true freedom consists in the acceptance of principles, of laws which are their own, a synthesis of universal and particular interests becomes possible.” [web]