Newegg offers the Lite-On USB 2.0 External DVD-ROM Drive, model no. eTDU108-32, for $18.99. Coupon code "ESCKAAT68" cuts it to $9.99. With 99 cents for shipping, that's the lowest total price we could find by $7, although we saw it for a buck less three weeks ago. It reads DVD-ROM media at 8x and CD-ROM media at 24x. Deal ends October 12.
Note that this drive doesn't burn discs.