MUGEN
Mugen Dev Forum - The most alive forum about mugen to date.
Mugen & Hentai - This is where I first learn about mugen. This site has something not for minor. :)
OolongV's MUGEN BOOKMARKS - The most complete links about mugen to date.
MCM - A great tool that make life easier for sprite development.
Zero Gravity Studios - A great site featuring two useful tools and great creations.
GAMING & EMULATION
The Madman's Cafe - Get latest news about the gaming world here.
[ Retrogames ] - All your emulation needs.
If you don't want to see your site listed here, then please feel free to let me know.