I currently use Cubase SX3 which is high end and overkill for most applications unless you are producing music.
Steinberg (the makers of Cubase) do have some entry level software if you are wanting something reasonably comprehensive.
Audacity is a good choice, Hyperengine AV by Arboretum systems is a free Mac programme which has worked well for me.
A good idea is to look up Versiontracker - there is an absolute treasure trove of freeware, shareware and commercial material out there if you know where to look.