If you're one of the lucky generation, like myself, that grew up playing Space Invanders and Pac-Man on an Atari 2600, you'll love this Atari site that includes rarity information, screenshots, scanned manuals and ROMs. They've even gone to the effort of scanning in the cartridges themselves so you can remember what they look like (if you don't still own them).

Excuse me while I lapse into a nostalgic trance.