OK, I'm answering your PM on the thread for everyone's benefit.
SX-70
The SX-70 is the forefather of all Polaroids. It's a self ejecting, manual focus (later models had auto focus, with a manual over-ride) SLR Polaroid. All those Pola shot in focus were most likely taken with this modern marvel. But they stopped making them in the early 80's I think. They used two kinds of film, SX-70 and Time Zero. Both of these films are now extinct. 600 film can work with this cam, but the camera has to be slightly modified, as shown here:
http://www.foundphotography.com/PhotoThoughts/archives/2006/06/polaroid_sx70_modification_for.html
SLR 680 and 690
These cameras are pretty much super SX-70's that take 600 film, so no mods are required. The problem is they're rare and nerds like me and others want them bad, to the tune of $150 or more each on eBay. I can't justify the cost to practicality ratio of these things. You can get an SX-70 for $20 at times, a little rough around the edges, but definitely usable.
Polaroid 600SE
This thing isn't even made by Polaroid. It's a
Mamiya Universal with a 3x4 inch pull-apart film back. It has interchangeable lenses, full manual controls for shutter, aperture, and focus. It has no electronics, not even an exposure meter. It weighs as much as a third arm and is nothing short of beautiful. Not only does it use 3x4 backs, it can accept 6x7 and 6x9cm medium format film backs. All the backs have dark slides so you can switch film mid-roll. I THINK everything is compatible with the Mamiya except the lenses. There's also a Polaroid 600 that has a fixed lens. These things start at around $450, but it's well worth it. Oh, and it's a rangefinder too.
Polaroid Spectra
And last is this rare gem, the Polaroid Spectra system. It shoots bigger than the SX-70/SLR series, and the film is readily available. The REALLY badass ones have manual focus on them. They also have a timer, flash over-ride, all kinds of cool options. Another variation that's harder to find, but way cheaper is the
Minolta Instant Pro, which is actually pictured above, and is cosmetically exact to the Spectra.
foundphotography.com -- kenrockwell.com -- photofxdm.org -- camerapedia.com
All this said, I scored a Spectra in a thrift store in the original box for $7 and an SX-70 for $9 with the accessory kit. Just keep your eyes peeled, most people have no idea what they have.