Atari Age These wonderful people have tons of info on Atari 2600 and other Atari games, including screenshots, game manuals, game box art. They also have ROMs, but you have to unzip them.
Batari Basic Ever wanted to create your own 2600 games? Here's a great program that lets you. They work on emulators and actual Atari 2600 consoles! Wow!
Minigame Compo The Minigame Competition is held each year for homebrewers who submit 1k, 4k and 8k games for classic systems, including the 2600.
Moby Games Type a title of a game and it'll give you info about it. It might not have every single game on earth, but it has most of them. Works for almost every system ever made.
Rom-World Has Atari 2600 ROMs you don't have to unzip, plus alternate versions, and bad dumps for some reason. You don't have to be a member.
Video Game Music Archive These dedicated people make MIDIs for games of every single home gaming system you can think of (including the Atari 2600), and arcade games, too! Aside from having over 20,000 MIDIs, they also have a forum, where you can talk about video game music and put in a request. Anybody can post a MIDI and joining the forum is FREE!
Video Game Music Archive's nice button thingee.
Atari Atari's (formerly known as Infogrames) official website.
SMB1 Paradise A site also made by me that has a SMB1 shrine, plus reviews of Game Boy, NES, a few SNES, and DS games. And, there's MORE!
The Mushroom Kingdom Everything you need to know about Mario and his pals (and enemies.)
NES Player One of the few surviving NES-related sites. May not be able to get into at the end of the month because of bandwidth problems (people like the site too much!)
Other interesting sites
Geocities The site that hosts this fine page! If you want your own URL like mine, just give 'em about $5 per month.
Google The best search engine on the web.
Wikipedia The free online encyclopedia. Very useful!