some other good links i found:
I am fairly new to the mac, but have been using windows for years, and if you have the option to move some of your files such as movies, music, etc to another hard drive, that should speed up your system. i know you have 60gb left on the drive, but when the operating system has to manage all those big files as well your operating system is moving more slowly.
i use a separate partition for my files to keep it running more smoothly, but if you partition your drive within mac os x, then you would lose all your files. supposedly, the program ipartition allows you to partition your drive without losing your files...but you should backup your important files before using any kind of utility...just to be on the safe side.