Here below is a list of very handy OpenSource or Free Softwares. I am using all of them, and consider them as a good alternative to professionnal and sometimes expansive softwares.
None of them contains advertisement or spyware, and they are fully operationnal. Some of them doesn’t have the very same functions than their “pro” sibling, but learn how to use them correctly, and you won’t have to buy or illegally download the “pro”.
OpenOffice : The main challenger of Microsoft Office. Free!
Firefox : One of the best web browser. At least, way better than IE as far as I’m concerned
7Zip : A multipurpose archiver. Can open rar, arj, zip, and many others.
uTorrent : A simple and yet very accurate bitTorrent client.
Avast! : Avast! Is a free antivirus. You will need to register, but their Home Edition is absolutely free.
ZoneAlarm : ZoneAlarm is a very effective firewall. The firewall+antivirus suite is not free, but the firewall itself is.
FileZilla : FileZilla is a FTP client. Just as good as others, but free.
Wireshark (former ethereal) : THE network sniffer/protocol analyzer. A must-have if you have to work/test networks.
Putty : Putty is a lightweight and standalone tool to connect remote servers via telnet/SSH. Useful for server administration
Visual Studio Express Edition : An excellent development environment.
NVu / Kompozer : An offline HTML/CSS editor. Free alternative to DreamWeaver
PSPad : The ultimate text editor. Syntax coloring, spelling suggestion, TextDiff, hexadecimal editor, and fully integrated in Windows Explorer…
NSIS : NSIS is a script based setup generator. Very convenient to release your apps.
2D Design, photo edition
Gimp : Gimp is a fabulous Image manipulation software. The interface is a little perturbing at first, but you will be able to do in no time exactly what you liked to do with photoshop.
3D Modeling & Rendering
As for this section, I must say the free softwares here below are quite good, but nothing is even close to 3D Studio Max, Maya or LightWave. 3D modeling/rendering is the only domain free apps are no match for the commercial apps.
TrueSpace : TrueSpace became free only recently. It’s a modeler/animator/renderer, and it’s worth trying!
Blender : soon.
Music & Sound
ModPlug Tracker : A nice tool to compose soundtracks
Feel free to suggest me some free/opensource software you liked, I’ll update this post regularly!