Best way to compress wav files?

You can convert songs in your iTunes library to another format. When you convert a song in iTunes it will be converted to the format that you have set to import your CDs in. Converting creates a second copy of the song in the format you have chosen which gives you the opportunity to either keep or delete the original. If you are using iTunes 8 go to Edit>Preferences>General and click on Import Settings, change your option to MP3 for example. Go back to your library and highlight the songs you want to convert and go to the Advanced menu at the top of your iTunes window and choose "Create MP3 version": iTunes: How to convert a song to a different file format

One what do you plan to play them once compressed? Just your Mac, or will you want to be able to play them on other devices? A low-bit-rate AAC file would perhaps be the best choice for playback from your Mac, but for maximum portability, go with MP3.

If you choose AAC, the Spoken Podcast preset in iTunes' importing preference should be fine. For MP3, set to 32 kbps. In either case, convert one lecture and listen to it before you convert them all so that you can verify that you'll find the compressed quality to be acceptable.

Regards.

*How do I convert a file in iTunes*

Follow the instructions in the link I posted above

You're welcome, take care.