Yes indeed, iTunes will do this for you

(and it should be in the software forum!)
Import the tracks into your music library (just drag them into the window). At this point they will still be WAV's.
Highlight the tracks that you want to convert, and then go to the 'Advanced' menu, and go to 'Convert Selection to MP3/AAC' (It will list one or the other).
That's it!! Make sure to then delete the originals from the library. If the option you want isn't in the menu (if it says 'convert to MP3, and you wanted AAC' - go the the iTunes preferences and change the default setting under 'Importing'
Man, this is about the only advice I ever give in this forum, but I seem to just say it once a week and someone else will think I'm great
(next time I will copy-paste it I think)