Virtual CloneDrive is about the best (and free) imaging mounting utility that I have come across so far. It has been very reliable and lightweight on all XP and Vista systems that I have used it on. VCD allows you to mount ISO, BIN, and CCD file formats and allows up to 8 virtually mounted discs at one time.
Pound for pound, this is easily my choice for mounting image files. That’s all there is to it. To see how it works, check out my tutorial post on how to mount an ISO file.