Depends what you mean, if you mean surround from a DVD, then the Apple DVD player only supports stereo, although you can but 3rd party soundcards with outputs up to 7.1. You'll need a player that'll talk to the outputs though, I think VLC does. Games are supported ny the 3rd party cards.
If you mean surround in a recording/MIDI sense, then Apple supports multi output via a 3rd party interface like MOTU's 828 FireWire, or emagics EMI 2/6 USB, and pretty much all of the audio/MIDI sytems (Logic, CubaseSX, DP) support multi-channel output. ProTools obviously does, but only in the expensive HD system.
All Macs come with stereo audio output as standard, and most have stereo input as well.