These days I'm becoming a fan of open source software. Not because of the big reasons of "no one owns the code" and all, but for the simple reason that I want to avoid piracy and at the same time have the best of the utilities and software on my laptop. In other words, because its free.
And after some research, I've found various open source equivalents of software that otherwise would be hard on your wallet. Here are some website for the benefit of others.
http://www.osalt.com/: Open Source Alternative is what this site's name stands for. Here you can find almost all software that you're looking for.
www.downloadpedia.org/Open_Source_Alternative_to_Commercial_Software: This website (actually, only one page) is similar to the above and gives you more options. Downside is that it's not as organized as the above.
www.sourceforge.net: The mother of all open source. This website hosts numerous projects on open source platform. Fully searchable.
Whenever open source comes to mind, Linux is the next word. I tried it on my mom's laptop once, but well, am too used to the Windows UI.
Nevertheless, few other software that I like in open source are as follows:
GIMP: Image and graphics editing
Strokeit: for mouse gestures. (e.g.: right click and hold your mouse -> drag to make a 'C' -> the selection (if any) is copied). Okay not that descriptive, you'll have to use it to understand its utility (trust me, after sometime, you can't live without it).
Infrarecorder: CD and DVD writing
Clamwin: anti-virus for your PC
Winpooch: anti-spyware for your PC (many websites brag a lot of using clamwin and winpooch together for "excellent" protection; but I didn't find winpooch that friendly. It consumes 99% of my system's resources)
SumatraPDF: This one's a darling. Many people (myself included till sometime back) don't use any other PDF viewer as Adobe's Acrobat Reader is anyway free. But if you need to open as many huge size PDF's as I do, try Sumatra. Amazingly fast. Acrobat is way behind in speed.