I do pretty much what Nige does, though I may start with a 600 dpi scan. The results always feel unsatisfactory next to a print, but it's a way of getting some stuff out there.

Sometimes I'll make a digital dupe of the negative using a Coolpix 990 on a copy stand with a light box, invert it to positive in Photoshop, and then try to reproduce the quality of the print from there, and that usually works a little better.

For 35mm I have a film scanner (Minolta Scan Dual I).