Dick Lipton has a blog post that motivated this question. He recalled the Stark-Heegner

Theorem: There are only a finite
number of imaginary quadratic fields
that have unique factorization. They
are $\sqrt{d}$ for $d \in \{-1,-2,-3,-7,-11,-19,-43,-67,-163 \}$.

From Wikipedia (link in the theorem statement above):

It was essentially proven by Kurt Heegner in 1952, but Heegner's proof had some minor gaps and the theorem was not accepted until Harold Stark gave a complete proof in 1967, which Stark showed was actually equivalent to Heegner's. Heegner "died before anyone really understood what he had done".

I am also reminded of Grassmann's inability to get his work recognized.
What are some other examples of important correct work being rejected by the community?
NB. There was a complementary question here before.

Tarski ran into some trouble when he tried to publish his result that the Axiom of Choice is equivalent to the statement that an infinite set $X$ has the same cardinality as $X \times X$. 

From Mycielski:
"He tried to publish his theorem in the Comptes Rendus but Frechet and Lebesgue refused to present it.  Frechet wrote that an implication between two well known propositions is not a new result.  Lebesgue wrote that an implication between two false propositions is of no interest.  And Tarski said that after this misadventure he never tried to publish in the Comptes Rendus."
