Autodesk Miller (free until the end of the year) can convert gcode to STL (and also do some other tricks). Could be useful in a pinch or to reverse engineer something.
http://labs.autodesk.com/utilities/miller
Lots of nice “free” applications coming from Autodesk. They probably serve up an amazing slicer soon. Apart from closed source I’m a bit worried about how they will monetize this. They currently sell addon packages and probably get kickback from 3D printing companies, but I believe this is a purely for profit company, and I don’t trust them not to suddenly start to take ridiculous prices for the software. So unless you pay you’re models are stuck in a format you can not use …