One of my favorite games in the past few years has been Lemmings. I found a version of it online, saving me having to install it. It is still fun to play, figuring out how to get those little guys from where they fall from the sky to home. I found it at funnyGames.nl.
Another game site for old games is 1980 Games which has games like Donkey Kong, Space Invaders and Pac Man as well as others from the 1980s.