I've meant to learn more about the path tools in Photoshop. YouTube has a decent series of basic tutorials for using the path tools. In this first in the series, desktoppublishingsr gives an overview of the all the pen and selection tools:
Photoshop Path Tool Video Tutorial #1 — YouTube
I knew what all of these tools did, with one exception: the convert tool. I always wondered how you could choose only one of the handles. Now I know!