Yep, no cd cracks will work for single player, just make sure you get the correct version for the game version you are running, e.g. If your game is patched to 1.6 you'll need a 1.6 no cd crack
There is also Megagames
The cracks are usually listed as "Game Fixes"
If you want to go with your original idea you can create the .iso files and mount them in a virtual drive, there are a couple of programmes to do this with, names escape me right now as I use no cd cracks personally.
This is a topic that is hotly debated in most forums as you are technically breaking the EULA by altering the game code and is the way people can use pirated games but on the other hand people (like myself) who have bought the games legitimately will argue for the use because of the reason you state and the fact that continual use scratches the media eventually rendering it useless.
There are several game makers/marketers who realise this (THQ - Company of Heroes for example) who have a no cd built into the game, but however you may randomly (usually after a patch) be asked to insert your disk to verify ownership which imo is a much better system