Old-school Game Of the Day. Each day a different screen-shot of an old-school game, along with a brief explanationNote: The original idea is from the "Astronomy Picture of the Day" NASA website, just transposed it for games, not maintained.
A personal selection of 140 recommended games in screen-shots of the Sega Megadrive/GenesisNote: Flash required.
Old forum with lot of resourcesNote: Not maintained.
Sega Master System
SMSPower; Sega Master System Community
Meka; Great multi-machine emulatorNote: Awesome if you want to code/hack for Sega Master System/Game Gear, great set of tools.
RetroCopy; Accurate home consoles and arcade systems emulatorNote: I dig this one for its accuracy.
SegaXtreme; Sega Saturn/Dreamcast dev. community
Sega Saturn related resources (docs, tools...)
Yabause; Great Sega Saturn emulator
WLA-DX Multi Platform Cross Assembler PackageGreat assembler for old-school consoles coding.
Brackets; Open Source code editor for web designers and front-end developers.Note: Complete and very lightweight.
CodeLite; Open Source Cross-platform IDENote: Complete and very lightweight.
Notepad++; Awesome open source sophisticated text editor. (Windows only)
Official OpenGL website
zophar.net; Docs and tutorials of older systems
NeHe OpenGL tutorials
scene.org; Demoscene portal
French demoscene bbs
Tool Command LanguageNote: Great choice if you want to make small to medium cross-platform applications.