There is a great article on linux.com (you didn't expect such a link here, did you?) titled SysAdmin to SysAdmin: It's the documentation, stupid! It is about a topic that is close to my heart: developers don't like writing documentation, and keep telling you (user) that the source is the documentation - which I couldn't agree with less, even if I am a programmer-user.
Now though this article is targetted at Open Source projects, you will agree that you too have seen less-than-stellar documented projects in companies (even yours), or you had to work with third party software whose documentation left to be desired. How did you feel when you had to find out how to achieve a task? Right.
Having this said, I'd like to offer a great starting point for writing technical documentation: quite some time ago, Bernd (de) wrote an article titled Technical Writing Made Easier, specifically targetted at programmers. Check it out.
A Channel 9 video where Anders Hejlsberg talks about the future of programming data in C# 3.0.