There's truly a lot of people and groups that deserve credit for what you see here.
Firstly, the application designers and maintainers for which themes are used for in the first place. Your efforts in creation and maintenance don't go unappreciated!
Secondly, to the themers that have spent their time in dreaming up new ways to theme/skin those applications. There's some pretty creative and talented people out there!
I'd also like to thank the following list of companies/groups of which this site wouldn't exist without.
Last, but certainly not least, I'd like to thank the following for their incredibly useful and necessary contributions to the OpenSource community. They have, in large part, helped me bring all this theming stuff together.