Freemind – Mind map program. Some schools encourage their students to use mind maps. Requires Java JRE 1.6 and above.
RoyalTS – Terminal service program. Enables you to simultaneous connect via RDP to multiple computers. This was open source, from version 1.4.x it is closed sourced. The free versions allows a maximum of 10 connections. Also covered here.
Gimp – Graphics editing program This is a fully featured graphics editing software. Can be quite intimidating with its functions and layers. Once you familiarise with the user interface, it really rocks.
Sysinternals – System Internals of Windows. Enough said.
Robocopy – Robust copy, part of Windows Resource kit. A great live safer for file server migration.
Ghostscript – PDF converter. It takes PS files and converts into PDF. This is freeware, even for commercial use. PDF995 engine is actually Ghostcript.
Update 16 Dec 09
Portable applications are programs that don’t require installation. All the executables and libraries are placed in a folder of your choice. Outside the system folder. This can really save the day when you have computers that are locked down due to security policy and what you have can’t do the job.
Thunderbird POP3 email client
Freemind mind mapping beta version, 0.9 beta9
VLC Video LAN
1 Apr 10
Keepass An excellent password manager for all the network, forums and websites. A portable version enables you to put it on a USB stick. The database can be secured by master password and/or key file. If for some reason, you can still view the original password. There are two versions available. The Classic Edition (1.17)which really lightweight requires nothing from the operating system comes with 2 types of encryption, The Professional Edition (2.10) requires Microsoft .Net Framework 2.0, comes with more features but only 1 type of encryption. link
Update 28 Jun 10
Truecrypt Personal data encryption. Create a file of a predetermine size to be your virtual disk. Put your stuff in. This is available in portable and installed version.