WinRAR is great, it just has an (arguably) annoying thing about it, it's not free...
And while I'm at it; Here's another little tidbit I seem to have forgotten:
Startup Delayer - Make nonessential software wait before they launch at startup. It cut a good 30 seconds off my boot time, so it's DEFINETELY useful.
And I forgot my all time favorite audioplayer...
Foobar2000 - It supports Windows Audio Session API exclusive mode output support through
WASAPI plugin (Vista SP1 only!) for unparallelled soundquality. Imho there's nothing that sounds better, and with the right tweaks it can even look better.