If you find that your Mac’s Superdrive has stopped working, or you’ve replaced your internal Superdrive to fit a solid-state hard drive and need a cheap way to get a working CD and DVD reader or recorder, your options are a bit limited.
However I’ve found these Samsung External USB DVD-Writers to be reliable, inexpensive and work with OS X 10.5, 10.6 and 10.7.
P.S. The only trouble you’ll have is getting it to work with Apple’s DVD Player application. However this hint worked for me beautifully.