Been playing with Hugin and qtpfsgui both are free, though I'm not 100% sure of the licensing of the tools. With a small bit of work I think you can get some pretty cool photos without having to pay for commercial software. They may or may not be as powerful as the commercial alternatives depending on what you like, but at least these two tools are cross platform.
Rawtherapee is another free tool for anyone who takes raws from their DSLR or high end point and shoot cameras. Now all I need to do is find some nice free and cross platform photo management software. 'ls' comes to mind.