I get tired of renaming/copying/backing up various JARs when trying out snapshots. I haven't been able to find anything to help me bypass this renaming issue. Can I get Minecraft to launch different JARs?
I use MultiMC, it works on Windows, OSX and Linux and allows you to run many instances of Minecraft from a single launcher.
It even allows you to automatically install mods to individual instances and have different save files for different versions.
Nevermind, apparently Magic Launcher can do this!