I made an external DVD drive from some spare parts I had laying around:
a.) Pioneer OEM DVD/RW 5.25' internal SATA drive - $15 from Microcenter
b.) No-Name 3.5' SATA to USB 2.0 hard drive enclosure - $8 from a woot-ripoff etailer that's no longer around
It looked pretty sketchy(Optical Drive was sittin out in the open on top of the encolsure's circuit board, be carefull where you touch) but it worked like a charm for installing XP nlite over Ubuntu after failing 50 times with 25 different 'USB methods'. If you just need to read a disk every once in a while, you can do that, just make sure the hard drive enclosure is USB 2.0 and not USB 1.1 as 1.1 speed won't be fast enough for some applications. Don't know how that will work with OSX but it's worth a shot as most people have these parts lying around.
Of course if it's something you want to carry this with you to Starbucks and look cool, this would not be a good idea. Unless it's a Starbucks filled with hackers and modders, then your stock would rise.