Use the magic launcher, not only can u have multiple setups, you keep your minecraft.jar clean, it just adds the mods while u play and removves when its done. You can also allocate ram so much easier with this. I use this for opticraft.
Got a setup with only optifine for opticraft
And a Super Modded one for me and Morgans server
And i got other random setups like the snapshots and so on.
Give it a try