Video Applications of the SM57?
 

I finally bought a shotgun mic for my camera after and an adapter to go along with it. I have an sm57 that I use to record music and was wondering if there are any good uses for this tried and true mic in video applications. I figured maybe live music performances would be one (correct me if I'm wrong) but are there any other uses as a backup to the shotgun mic? I'd hate to see it not being used when it could do something productive instead. Thanks for the help.

It can be useful for ambience during a loud music performance.
You can also use it to mic a loudspeaker when you can't make a hard-line connection to a sound system.
With a good windscreen you can use it as a handheld interview mic.
Lastly, if you only have a poor acoustic space to record in, you can use it for voice-over recording. Again it needs a good windscreen and you have to employ it correctly to get useable results for this since that's not what it's designed for.
If you need to record an electric guitar amp, then that is exactly what it's designed for.
There are mics that perform these functions better and are also low in cost, like the Sennheiser e835. Obviously there are a lot of much better mics for these functions too, at a much higher cost.
Welcome to the world of building a mic arsenal.

Why does the 57 need a windscreen for voice overs?
And is it true that the SM58 sounds the same
as the SM57, but the 58 just has a built-in
windscreen?

They both use the same cartridge, yes.
The windscreen provides the proximity effect with out the direct access to the plates inside.

I remember from a NAMM show a few years ago, that Shure claims that every President except 2 have chosen the 57 as "the" Presidential mic, since the 57 was first manufactured.