sys 6.0.8 or 7.0.1 (or 7.1) are probably what you're best bets are in terms of System software.
As for uses? -- try it out, you might be surprised. I found that a basic mac could still help me accomplish 90+% of what i *need* to do (word processing, spreadsheets, graphing, email, etc). MS Word 4 or 5 (5.1a was the best), WriteNow 3 or 4, CricketGraph, MacDraw, MacPaint, etc...plus lots of classic games (lode runner, risk, glider) run very well on an 8 or 16 Hz chip.
You can even hook one of those up to the web (albeit with a little bit of work) and surf (with an appropriate non-graphic browser -- like WannaBe). I had to survive for a bit while my 'book was temporarily out of commission -- so dug the SE/30 out of the closet and had a lot of fun. The B&W was somewhat limiting -- but for text web pages (or low graphic versions), you'd be surprised how fast they can load.
if indeed it is a Mac Classic -- Sys 6.0.3 is stored in ROM, so you can boot up into a system by holding some combination of keys (command-option-X-O, if i recall -- "XO" was one of the codenames for the Mac Classic).
cheers, enjoy....