Yes, Buzz Lightyear and Woody are at Disney World. There are also many other characters that you can meet while there. Including Winnie the Pooh and Friends, Mickey and Friends, Princesses, etc.
You will find Buzz in Tomorrowland in Magic Kingdom. He will usually be in the former Time Keeper lobby. Also keep an eye out around the Buzz Lightyear Spaceranger spin ride.
Woody and his gang is at the Diamond Horseshoe in Frontierland, also in Magic Kingdom. Woody, Jessie and Bullseye are usually there.
Hope this helps
EDIT:
I also forgot to mention something else. There is a rumor that there will be a new character breakfast in Disney. It's supposed to be popular like Cinderella's Royal Table in the castle for girls, but this one is going to be more for boys. It is going to be called Breakfast and Beyond. It will be at Hollywood and Vine in MGM Studios for breakfast. It is supposed to premier on April 1st. The characters that are planned to be there is Buzz, Woody and the gang, but this is not set in stone yet. If you like Buzz and Woody, I do, this will be a really great character breakfast to go to. I hope that it comes out as planned.
EDIT:
This was just released:
Timekeeper to Close! Effective February 26, 2006, this Tomorrowland attraction will officially close for good -- a new attraction for this location is being developed and details will be announced in the future. Character meet and greets with Buzz Lightyear and Stitch will be relocated in Tomorrowland, while The Incredibles are slated to return to the Disney-MGM Studios.