It is possible to install fonts in your MacOS X account. This means that the font will follow you from one computer to the next, but will not be available to anyone else.
This document explains how to do this and lists several caveats.
Note that each font that you install uses a small amount of resources. Therefore, using a lot of fonts will slow even the fastest computer.
Note that just because you can see the font, it doesn’t mean that anyone else can. So if you make a document that uses one or more fonts that you installed and then send it to someone else, the document will probably look wrong (i.e. ugly) when they open it.
Note that in order to preserve system stability, we reserve the right to remove fonts from your account without prior notice.
Note that new fonts may not be available in a program until after you quit and re-run that program or possibly until after you logout and login again.