Inkscape lets you create and edit vector based graphics, which are – other than bitmap graphics – indefinitely editable without any loss of quality. You can resize, recolor or reshape graphics without losing sharpness or adding noise. Inkscape even lets you open PDF files and export any graphics you see. If the image embedded in the PDF is itself a vector image (e.g. MESH art), you can start playing around with the art, change color etc (always respect brand guidelines!).
2. Foxit Reader
This PDF reader is a great alternative to Adobe’s Reader software. Not only is it very lightweight and fast, but it’s also much more secure than the Adobe Reader. Foxit Reader even lets you highlight text, add text, add arrows etc. right inside the viewer.
Rated the best open source project in 2007 by SourceForge, 7zip may well be THE best packer/unpacker on the planet. The installer comes with a weight of only 1MB and still gives you everything you expect from an archiving tool: Context menus (“extract files here…”, “add this file to a new ZIP archive”, …), extensive file type support (including .rar) and loads of settings.
Although I would not consider this a true Photoshop alternative, GIMP is still a very powerful piece of image editing software. Layers, filters, import/export options… you name it. If you’re used to Photoshop and can’t quite adapt to the GIMP interface, try GIMPshop, which makes GIMP look and feel more like Photosohp. If you’re more used to paint, try paint.net, another great free image editor.
5. SyncToy & TrueCrypt
Although these two are different tools, I join them under one purpose: Backups. If you don’t back up your hard disk, you’re in constant danger of losing all your data from one second to the next. Hard drives fail. Period. However, merely copying all your documents to an unencrypted hard disk is not exactly the way to go either. The combination of SyncToy (a Microsoft tool which lets you create folder pairs which back each other up regularly) and TrueCrypt (the ultimate encrption tool, recommended by security expert Steve Gibson) is a free, yet very secure solution to your backup needs.