Open Source software is becoming more and more popular even though, many of these applications are little or none known at all.
There are browsers (eg: Firefox, Chromium), application suites for word processing, spreadsheets, presentations and other (eg: OpenOffice, kOffice, Gnome Office), video and audio players (eg: VLC, MPlayer), editors for vector and raster graphics (eg: Inkscape, GIMP) and many, many more.
Some people might complain that not all of this software is as good as the counterpart to pay but hey, this is open source software. You can download it, install it, give it a try and keep using it if you like it. Otherwise, simply uninstalling it and keep looking for something more suitable to you.
No license to pay, no free 30 day trial and, I'm sorry for those of you who used to enjoy it, nothing to crack! :-)
Enjoy this article on the 10 Greatest Open Source Software of 2009