One should always briefly explain what (the PC program) actually does. Most of us don't use PCs.
Hypercam itself is not made for Macs, but there are at least six similar programs out there, probably more advanced actually.
If you are running Snow Leopard (10.6.x), you already have one on board: QuickTime X can make full screen recordings which you can then edit in iMovie or some other program, and of course from there you can upload directly to YouTube (or indirectly to just about anywhere).
If all you need is to capture your full screen, QuickTime X is all you need.
For more elaborate screencasts, I like
Screenflow from Telestream or
Camtasia from TechSmith. There's also Snapz Pro X, iShowU (and iShowUHD), Sequence and others.
At ACDSee we use Camtasia for screencasts.
Here's an example.