You need an interface between the computer and microphone. There are tons of threads on the best interface here and they come at all price points. I use a Toneport UX-2 which has two microphone inputs w/phantom power and two instrument inputs. You wouldn't need phantom power with the SM-57. They also make simpler devices like the Blue Microphone Icicle (see below).
I'm in the market for something as well. I've done some reading, and apparently the Rane MS 1S is a pretty good 1-channel preamp. $200 USD new, so not exactly in-expensive, but I have a hard time buying something cheap that has a bunch of features I don't need and sacrifices quality for it. With that in mind, I haven't heard this preamp, so I don't know exactly what to expect.
You'll need an analog to digital converter as well (which I'm also in search of). It would be nice to find something with one or two inputs to go along nicely with the MS 1S, but I haven't fully researched them yet. There are interfaces that have mic preamps and ADCs in one unit, but decent ones seem to be at least $600 for a few channels. You could get something for $300, but from the reviews I've seen, people have a lot of problems with most of the models, or there aren't many reviews out there to base their quality on.
You really need to define your requirements to answer some of the questions coming up, my first post was referring to a home recording setup to make good quality recordings. If you need professional level recordings you will be getting into individual preamps and a whole host of other gear.
Here's a review by Craig Anderton of the interface I use that gives you a lot of functionality for a few hundred dollars (it's fairly old but still accurate).
By the way, I'm not trying to say that's a great interface or you should by a UX-2...it's just what I'm familiar with so using it as an example...plus Craig does great reviews!!!
Figure out what you need and how much time (and motivation) you have to connect and dial in equipment. If it's just a hobby and you're getting your feet wet start out simple and learn the ropes, it's easy to move up when you need to and you haven't wasted a lot of money on gear while you're figuring out what works for you...
You can find a used M-Audio Duo pretty cheap. Two decent preamps, USB into your computer, SPDIF digital out, can be used as just mic pre or just as AD converter. Only supported on XP -no Vista or 64-bit drivers.
i'm a little bit late on this thread but i looked into the icicle by blue and it's a signal converter and a preamp so it does both. i have not tried it yet but it seems like a good deal. http://www.bluemic.com/icicle/
if you have a bit more money i would suggest getting an mbox