Audcacity

is probably the leading sound-editing freeware on the internet. It lets you do everything - record, modify (wanna sound like Alivin and the Chipmunks?), and export to WAV, MP3, or OGG. I have used it for many things, including recording for making movies. Go to this website to download.

Credit Maker

In Windows Movie Maker, I found credits to be - let's face it - lame. If I wanted something like:

CASTING

John Johnson

Peter Peterson

CAST

Ed William Wonderous

Mary Anna Banana

you would have to have the "Casting" go from bottom to top, and then the "Cast." from bottom to top. With Credit Maker, you don't have to wait for one section to be finished for another one to begin. It exports to avi, and can be downloaded here.