Yeah, Win 95 will run on it, but it will be fairly slow if you don't upgrade the memory, at least. Don't even try win 98. I tried it on a P100 with 48 MB, and it was unbearable.
I don't know if you'd want to spend this much time/money on it, but you could get a 32 mb chip and an upgrade processor like an evergreen or trinity works powerstacker 5x86 very cheap on e-gay, or in the forums here. Win 95 would be just fine on that. With some luck, you could probably get both for $25-30.
I have an old 486 with a trinity works 5x86 133 on it, and 36 mb ram. It runs win 95 great, as well as all MS office progs and email. Plus I still play starcraft on it. Web surfing is ok too, as long as you don't have too many windows open. 486s are still ok for that kind of stff. My 486 seems more responsive than my sister's P100.
I don't know too much about Linux, but it seems that almost everyone says it flies on a 486. You may want to check that out.
Believe it or not, I used my 486 from Feb '94 until Feb '99, which is when I got a used P166MMX. Then I biult my Athlon system. Even though I still use the latter two the most, the 486 brings back very fond memories every time I turn it on.
Regards!