The best thing you can do with that machine is install more memory. If that is a "quicksilver" machine, then max is 1.5 Gigabytes. Second best thing is a hard drive. It will take up to a 128 Gig IDE drive without a special utility program for the hard drive.
Check out
www.lowendmac.com for great info.
If you will be running OS X on that machine, I don't think you have to worry about crashes. I have a G3 iMac, 700 mhz, 1 gig ram, 80 gig hard drive. It runs OS X, the latest version without a problem, I also have CS2 suite on the machine and I have yet to see it crash. It runs a little slow on some things, but it is a 4 year old computer.
A 4 year old iMac running the latest operating system and CS2.
Gotta love it.