Earlier in the year, when they were filming X-Men First Class, there was a rumor that someone saw Hugh Jackman on the set. This rumor was later denied, but it still festered in the minds of many fanboys. Now it’s been confirmed that Hugh Jackman does indeed have a cameo as Wolverine in the movie. ComicBookMovie has the details:
Half way through X-Men: First Class, as Professor X and Magneto are travelling the world looking for mutants, they come across Wolverine, played by Hugh Jackman, in a bar. Before they can get a sentence out, Wolverine, without looking at them tells them to “Go [frick] yourselves.” They leave.
There is also confirmation of a second cameo of a character/actor from the original three X-Men movies; although exactly who is unknown so far.