The simplest method is to go into the properties of each of your user libraries (my documents, my videos, etc) and change the library location to another drive.
There are a few other methods as well to move your Users and ProgramData folders, but there are some minor glitches that result from this (after 1.5 years with this setup I think my only one is that I can't get my MS user experience score, it's pretty seamless but not perfect).
The best method has to be done when you install windows:http://answers.microsoft.com/en-us/windows/forum/windows_7-files/win7-how-do-i-move-user-folder-to-a-different/565f16a5-e5ed-43c9-8422-4f56aebb296e
They can also be moved after installation with this method (though be aware I don't think this works quite right, I believe the robocopy needs to be done as "robocopy /mir /xj" without the copyall):http://lifehacker.com/5467758/move-the-users-directory-in-windows-7
I would use this one at your own risk, I've used it, but it's also cause me quite alot of headaches in setting it up. (Once it's done it works great, but be careful not to lose any data).
There are also some registry hacks you can do, but I've never used them, so I can't make any recommendations.