UFC 124 Live Streaming: How and Where to Watch the Event Online
The action's already underway, but you'll have to go surfing to find it as the televised portion doesn't start until 7 PT. Or you could just wait another 40 minutes for the sanctioned live streaming to start on UFC.com.
But patience is never a virtue on the internet, so here's a link that's showing the unaired preliminaries (or promises to do so) to keep you occupied until the main attractions step into the Octagon. Better hurry, though, because they're only a couple scraps left and Matt Riddle has already logged a little time with Sean Pierson in the cage.
Incidentally, the last time it was this difficult to track down the prelims, it would appear they just weren't shown, period. In other words, no promises.