Both Damn Small Linux and Puppy Linux would work great on a 80mb drive. Each download is only 50-60mb and I keep DSL and Puppy on those mini-CDRW discs for easy access.
You'd be suprised what all is included with the OS. Obviously, they don't have the features of the full-featured distros like Ubuntu, MEPIS, etc., but I was so impressed with DSL, I thought about putting it on my laptop since it's so lightweight.