Linux:- www.linux.org -- is a Linux main resource site.
- www.linux.org.uk -- English site about linux.
- LFS -- if you want to dive deep in to Linux core.
- www.kernel.org -- Linux kernel archives.
- www.linuxjournal.com -- Linux magazine.
- www.linuxfocus.org -- Linux magazine.
- tldp.org -- Linux Documentation Project.
Windowing environment for linux and unix:- www.xfree86.org and
Window managers:- ION
- www.xfce.org -- Xfce homepage.
- www.gnome.org -- Gnome desktop.
- www.kde.org -- KDE desktop.
- A Slightly different approach to desktop by Sun.
I haven't tried the last one, it looks good, but requires a lot of processing power.
I currently use ION, because it is simple and fast, and does exactly what I like a computer to do.
Gnome and KDE are too heavy and big for maximum productivity on slower machines
Programming:- Php, programming language.
- Mindview, Bruce Eckells books about programming
- Brainf**k programming language.