When I bought my MacBook Pro a couple years ago, I didn’t get the largest hard drive available for it (in retrospect, a mistake). Between my music collection, digital photos, and Parallels PC disk image, 150 GB got close to full quite quickly. As a result, I’d been looking around for a way to archive some content (at least some music and photos) to an external drive to make more room.
I came across this old post that gives you a quick-and-dirty way to archive the photos (even if it doesn’t preserve the libraries). What’s especially convenient about Time Machine in this case is that if I find a better way to do it, I can recover the old setup from it and then archive properly.