OS/2 / eCS
OS/2 World An international collaborative community with free hosting for OS/2 or eCS related sites. (They are also hosting my programs C-Side & Labela).
eComStation eComStation is the new OS/2 made by Serenity Systems, based on OS/2 Warp 4.
Hobbes OS/2 Archive The ultimate location for OS/2 software.
Linux
Ubuntu
Ubuntu is the premier Linux distribution, there are many other distributions, but this one is probably the most userfriendly one.
Linux.org
Linux.org is a great place to find information about Linux and the different distributions.
Linux.com
Another great place to find Linux related information.
LinuxQuestions
If you have problems with your Linux, or just have some questions this is the place to look for help.
Qt
Qt (pronounced cute) is a cross-platform application and UI framework for developers. I'm aware this isn't strictly Linux related, but for me it is, as I'm only using Qt for my phones (Maemo (Nokia N900) and Meego (Nokia N9) ) and now and then for some Linux desktop development.
Maemo
Some years ago I bought an Nokia N900 phone. It was a dream come true, a real phone, with a linux based open source operating system called Maemo, not some plastic toy from Apple, Google or MicroSoft. It gathered quite some followers, but unfortunatly Nokia dropped it in favor of the Meego based Nokia N9, also a great phone, and still Linux based open source, but it lagged something. Lately Nokia (in their infinite stupidity) decided to drop all operative systems they have been working on for many years, and base all their future phones on Windows phone. Bye Nokia.
Lazarus
Since I upgraded from Basic and Assembler to Borlands Turbo Pascal, many years ago, I have prefered Pascal to C or any C like languages, which to me seams like a language developed by dyslexic people for people who cannot read. Lazerus is an open source pascal enviroment much like Boelands Delphi, but free. It's not strictly for Linux as it is a multi platform development enviroment, but I only use it for Linux development.
XBMC
XBMC is the great home theater system I'm using for my multimedia center, again not strictly Linux, as it exists for many platforms, but my media system is Linux based, so ..
Other computer related
Get Firefox!
Motzilla FireFox
The greatest browse on the web, try it.

Kompozer

Kompozer is a great tool for designing web pages, it is the opensource alternative to frontpage and similar programs.
Other links you might be interested in
OpenStreetMap OpenStreetMap is an opensource mapping initiative. The idea being that people like you and I map the world, and anyone  may use the data as they want (to mape maps, in research or whatever), as long as they do not sell them (as opposed to maps from Google, krak, KMS or Tele atlas). Why not join the community ?
If you have to ask, then don't bother ! This is very Danish comedy, and mostly for the Danish speaking.
The official LEGO page The gratest toy in the world - after the computer & playmate of the month - have a homepage, try it. 
Foder My family has a homepage, primarily used to publicise the result of oure geanology research, but it is also a messageboard for the members of the family.