Ubisoft has patched the PC version of Far Cry 2 to include proper widescreen support.
Previously the game did the old trick of cropping the top and bottom of the image rather than filling in the borders - something that BioShock was also attacked for last autumn, which led to a patch there as well.
Far Cry 2's patch 1.2 - check the Ubisoft forums for a list of mirrors - is a 51MB download that also deals with multiplayer bugs and balancing issues.
There's a full changelog through the link above, but it mostly sounds like common sense fixes ("Fixed the direct join by IP functionality", "The distance from a wounded team-mate is now displayed").
Check out our Far Cry 2 Triple-Format Face-Off to see what we made of the PC version compared to its console brothers.