I have used this tool so much in the last few days it's ridiculous. SlySoft makes Virtual CloneDrive, which allows you to mount ISOs right from Explorer. I've then been sharing the virtual drives for faster OS installs - using the network is the only way to go as opposed to a CD or DVD drive. Sadly CloneDrive won't work in Vista x64, but that's what virtual machines are for.
One other tool along these lines is ISORecorder, which allows you to rip CDs and DVDs straight to ISO.