Well, it would be totally illegal to download it, but *coughcough* you could use bittorrent or one of those other fancy programs to find episodes.
You could just watch it on television- although you would lose some of the story arc from watching them out of order, the show itself is enjoyeable to watch.
You can buy the episodes on iTunes. Cheap, I think.
Of course, when the show was on television, they aired "The Train Job" first, and then the Pilot in two seperate episodes. It was kind of weird, because it was this brand new show, and there was very little introduction, and then in the second episode, things were happening that had already been resolved in the first episode. That was why Fox sank it's own show.
I would reccommend finding someone who has the DVDs, and watching them with a group. Browncoats are notorious for sharing thier firefly, and it's a good way to meet a big group of nerds. Or, if you wanted to make the russian girls like you even more, buy it and watch it with them.

-kv