You can go to distrowatch.com, or linux.org & look at the distributions search page there, but unless you knwo what you are looking for, it could be awkward.
Also, I take it you're fairly new to linux, or else you wouldn't be asking such as question - so a straight forward Linux-on-a-floppy, might be a bit too basic, that is, just a straight command line and nothing else...
1. What is your level of experience?
- So I don't insult you by saying things like "OK, turn it on..."
2. What do you want from the OS - Basic command line, X terminal, Full desktop/Windows manager, Coffee maker?
- this will help find the right distibution and add-ons for you.
3. What does you PC have? CPU, RAM, graphics adapter, modeom/network card, and so on.
- same as above.
4. What is you internet access like, for that PC?
- This will help with how much you can download/install at any one time. You might be able to boot from floppy and install straight from an ftp mirror - it beats copying 400+ floppy discs at work...