Microsoft Office Picture Manager - for minor and quick edits on things I don't want to spend ages on.
GIMP - everything else.
I do have Picasa, but I never use the editing options. Just use it to track and view my photo collection on occasion.
I've never spent any money on photo editing software. There are plenty of free options out there that do everything I need them to. Lightroom does sound pretty amazing though, but I'd want to trial it before considering buying it.
I save all my money to spend on hardware goodies! I want a speedlight and a lens that goes a decent length over 200. Maybe swop out my 55-200 for something 70-300 or longer.