Moving A Library
If you wish to move one of your libraries to a new location on a single drive, iPhoto Library Manager will automatically track the library when you do so. Select the library you want to move in iPhoto Library Manager and click the "Reveal In Finder" button to reveal the library folder. Then, use the Finder and move (not copy) the folder to the new location on the drive. You will see iPhoto Library Manager update the path for that library as soon as you bring its main window to the front.
If you wish to move your library from one drive to another, you will need to copy the folder to the new drive and then add the copied library to iPhoto Library Manager's list. After you have opened up the newly copied library with iPhoto and confirmed that it displays correctly, you can go ahead and delete the original copy of the library. Another way to do this is to use iPhoto Library Manager's "Duplicate Library" command in the File menu to make a copy of the selected library on another drive.
While iPhoto Library Manager will track folders that are moved, iPhoto is not quite as smart. If you move a folder, make sure to bring iPhoto Library Manager to the front and verify that it has tracked the folder to its new location before launching iPhoto. Moving the library that iPhoto is currently using while iPhoto is still running is a very very very bad idea - don't do it. Quit iPhoto first if you are planning to move the currently active library.