I use lots of free software - my computer would be useless without them!
NetBeans - A powerful Java IDE which includes auto-complete and profiling
JCreator - a more light weight Java IDE, the 'lite' version, but still very useful
Google SketchUp Free - easy to use and powerful 3D sketching, model 3D buildings/etc for Google Earth or the Warehouse (also includes lots of free textures/models in some packs)
Super C - convert between many video / audio file formats (excellent)
can't remember if you already have these:
Google Desktop - Google tools and 'gadgets' built into a sidebar, indexes your computer and allows Google searches of your PC/Mac
Cobian Backup - a free, yet powerful backup tool - easy to use and includes encryption
Art of Illusion - a 3D modelling program, which is actually very powerful, although slightly harder to use than comercial software
forgot to add my latest addition to my free software library:
ChemSketch - excellent and invaluable to the chemistry student, a very advanced application that lets you draw molecules, equations, and save them to images, 3D molecule files, etc. Small molecules can also be named in the free version. BTW, be patient with the download process. You need to register first, and that takes 15min to process, and the download takes another 15min to process - but it does work.