I think this list is useful:

Burning Software:
http://cdburnerxp.se/download?lang=en

Office:
http://www.openoffice.org/

Graphics:
http://www.gimp.org/
http://www.irfanview.us/

System:
http://www.cpuid.com/hwmonitor.php
http://www.cpuid.com/cpuz.php
http://www.ccleaner.com/
http://www.7-zip.org/
http://www.safer-networking.org/en/home/index.html
http://www.almico.com/speedfan.php
http://www.larshederer.homepage.t-online.de/erunt/
http://www.techpowerup.com/gpuz/
http://www.kessels.com/Jkdefrag/
http://technet.microsoft.com/de-de/s...s/default.aspx

Video:
http://www.videolan.org/vlc/
http://www.codecguide.com/

Development:
http://www.wings3d.com/
http://www.microsoft.com/express/download/

Please add your recommendations.