The Plextor PX-708UF is an excellent external CD-R/CD-RW / DVD+R/DVD+RW / DVD-R/DVD-RW recorder:

It sports both USB 2.0 and Firewire interfaces, works great with my Windows laptop, and is kept in a corner until I need to record my monthly /home snapshot. Despite the fact that the Portuguese bundle has no Mac software (it comes with Nero), and that we can only get the silver model (none of the color versions are available here - you can only get the silver box), using it on a Mac is simplicity itself: Plug in, fire up Toast, pick the DVD format I want (usually mixed Mac+PC these days), drag the files in, and click "Burn".