Damn it, I thought you were going to say they're touring!
I've always thought that live albums are a good place to learn about a band, so I would recommend either "Different Stages" or "Exit... Stage Left" as a starting point. They changed their sound a lot in the 80s so suggesting an album from any time period won't really give you a good idea of what the rest of their material is like, so I think you should go with "Different Stages". It has three CDs, two of them from a show on the "Test for Echo" tour and another from (I think) their "A Farewell to Kings" tour in the 70s.
However, if you're not into live albums to start off with then I would recommend the following:
2112 - this is when they hit the big time. The title track is 20-something minutes long and is a classic.
Moving Pictures - this has their biggest hit, Tom Sawyer, plus a bunch of others. Probably their best album, or at least that's what the general consensus is. They changed their sound a hell of a lot after this, with less guitars and more synths.
Hold Your Fire - my favorite of the 80s albums. Quite commercial, and Aimie Mann does guest vocals on one track (which isn't a bad thing), but it has some of my favourite songs.
Counterparts - they changed their sound again with this one to a more straightforward rock sound. Less synths, but also no more long proggy songs like in the 70s.
So there you go. Personally I'd go with "Different Stages".
I don't know if you've heard any of their stuff. A warning - a lot of people really, really don't like Geddy Lee's vocals. I didn't at first but I got used to them and now I think he's great. He's also a friggin' awesome bassist. Alex is an underrated guitarist and Neil is, of course, one of the greatest drummers ever. Just watch one of his live solos.
I liked the documentary but I don't think their story is interesting enough to warrant a feature length film. Not much has really happened to them - Alex and Geddy formed the band, they recorded an album, got a new drummer, had a rough time with Caress of Steel, hit the big time with 2112, changed their sound in the 80s, changed back, Neil's wife and daughter died... and that's about it. Still, great to see a film about them and worth watching.
Here are some songs from each album I posted above (can't post the full version of 2112 because it's so long - they didn't play the whole thing live until the "Test for Echo" tour anyway):
So there you go, a small taste. For what it's worth, the first album I heard was "Exit... Stage Left". Took me a listen or two to get used to Geddy but after that I loved it.
