Now, bear in mind that I didn't (and I don't suggest that you) do anything illegal with your music. Using some music you own in a presentation isn't, as far as I know, illegal.
Now that that's out of the way, let me tell you what I discovered. In the past, if I wanted to crack iTunes DRM, it was easy, but it cost the price of one CD-R or CD-R/W. But on this particular evening, I was working in the living room and there were two flights of stairs separating me from my home office where my stack of blank CD-Rs resides. (The old-school process is, if you're wondering: burn the DRM-protected songs to a CD-R, then rip them back in.) Due not to the cost of a CD-R (pennies), but to the energy I would have expended climbing up and down two flights of stairs, I discovered a method of stripping DRM without ever leaving your seat and using, ironically enough, completely legal tools provided by Apple!
Here's what you'll need:
1. A Mac
2. iMovie or iMovie HD
3. A short quicktime movie
4. About five minutes
Here's how to do it:
1. Open iMovie or iMovieHD and create a new project
2. Import the song for which you want the DRM removed into iMovie(HD)
3. Import a the short quicktime movie*
4. Export the iMovie(HD) project, select "audio only" and choose your format (mp3, wav, etc.)
That's it! Bye-bye DRM.
*You need the short quicktime movie because if you try to import and export audio only from iMovie(HD), Apple will give you this funny little warning about how you imported DRM-protected music and you can't export it without adding some video. There's an easy workaround: add some video!