I'm sure that at least a few people on this NG own/use a chainsaw from time to time, so...
I've been wanting to get a chain saw sharpening tool, but wasn't sure what type to get - dremel attachment/clamp on angle guide/freehand file/etc... I ended up getting an angle guide/file kit made by Husquavarna from Lowes ($14). The kit comes with two round files and a flat file, a handle, and a small angle guide. The little guide is about an inch square and just sits on top of the chain, straddling a cutter. The guide aligns itself with the chain so that the correct angle is easy to obtain.
After just a few minutes spent figuring out how to use it, I was able to sharpen the chain in less than 10 minutes. I went outside to make a test cut on some recently cut logs - wow, this chain is scary sharp! Very impressive results with almost no learning curve and little time invested.
Anyway, for what it's worth, I'd highly recommend Husky's file kit.
Mike