Kristal - which i find to be simple, but works with plug-ins and gives me enough of a production palette.
[slight aside] does anyone else use Kristal? have you found that it offsets your individual tracks by a few seconds/bars after recording? it's my only gripe with an otherwise very cool little toolbox.[/slight aside]
Mthree Development's .WAV to .MP3 converter. it gets the job done and it's free.