I replaced my hard drive with a faster one and put the original drive as secondary. How do I change the destinations for the following folders: movies, documents, music, and pictures (all Finder folders)?
What do you want, just for those to show up in the left-hand pane of the Finder? You can simply drag the folders on the older drive there. If you want the pretty icons, you'll probably have to play with symlinks.
To change the location of your user folder an easy way is to use NetInfo Manager (it's in /Applications/Utilities).
Goto /users/<your_shortname>, click the lock to make changes, and type in a new home location. Then copy over your stuff (after a restart, I don't think it does this for you, but it's been a while since I did it).