If you use virtual machines on a daily basis like I do, hopefully you have come to build a library of ISO image on your system to be used by virtual machines instead of physical CDs for OS installations and such. Its so much easier to simply click on the CD I want rather than trying to find it in my cluttered office. The problem comes when I need to install some software on my host computer (think MS Office). Luckily there are nifty little tools to tell your OS to use that saved ISO file rather than looking for the physical CD. If you are using Windows the one I use is Virtual CloneDrive.
If youre using Mac OSX of course, the ability to do this is already part of the operating system, you just have to double click the ISO file and it will mount to your file system. In Linux just use your mount command to do the same thing.