A little while ago I made a post recommending http://www.slysoft.com/en/virtual-clonedrive.html to mount ISO images as drives.
But what if the disc image you have is not an ISO image - or if you just need some files from disc images every once in a while and don't want to have an additional drive show up all the time?
Try http://imagemaster.codeplex.com/. This small suite consists of one program to work with files in disc images which can extract files, create ISO images and burn to disc, and another one that can convert Bin Image Files (.bin), Nero Image Files (.nrg), Alcohol Image Files (.mdf), CloneCd Image Files (.img) and DiscJuggler Image Files (.cdi) to ISO images.

Update: It seems that the project doesn't exist any more at CodePlex, but you can still download the version 1.0.3.7 at http://www.softsea.com/review/Image-Master.html or http://www.freewarebb.com/files/file/7110-imagemaster/