Lots of companies have own their version of the SM57, but the 57 is the one that caught on. You rarely see 57s sell for 25-35 bucks (they are the one mic that there seems to be a strict blue book on, even used), and yet you can pick up some real sleepers made by other companies for very little money that do as good of a job as a 57, IMHO...
For example, I'd take an EV RE 15 over an SM57 any day, and I just picked up 4 for the price of a new 57.
The RE15 can be used anywhere you'd use a 57, and in most cases (amps especially), it excells...
Other EV sleepers--common and sometimes cheap: RE 16 (similar to the RE15, but with a vocal screen)...also the RE18, a great all-around mic...
The AKGs that kinda look like a 57 can be had for next to nothing, and sound great. I believe the model #s are D1000, D2000, etc. The D19 is a great all-around mic, but because of the Beatle connection, is selling for absurd prices...
The old pre-57 Shures that look like 57s are great sounding mics, and, again, I prefer them over the 57. The 545 comes to mind, especially the ones with the built in handle/clip.
Anything made by Beyer is worth checking out. I picked up a M422 brand new for 50 bucks in a guitar store (it had been sitting there for years with a 109.00 pricetag), and it just kills on snare. The Soundstar series is also worth checking out, both the ones that look like an SM 58, and the 421 clone. Both great mics, and very versatile...
The point is this...you can sell your 57s/58s on ebay for 70 bucks a pop and double your mic collection very easily by keeping an eye out for the mics that slip under the RADAR. And in most cases, your sound will improve, too.....