Now citrix has a community driven web site that can help tell you if an application will run in a citrix environment or not. Users can submit the application and in what configurations it worked and the community can vote, digg style, on each application and configuration. The site is just getting started but it already has 858 3rd part applications and 5395 votes.
Citrix really gets it when it comes to using and getting their user community support.
Citrix Ready Community Verified