Reading Usable Help
@UsableHelp on Twitter
Gordon R. Meyer
Try DITA online
If you're thinking about adopting DITA for documentation authoring, you'll need an editor that's DITA-aware. DITA Storm from LogPerspective is a popular option, and you can use a browser-based version of the editor at their website. Frankly, I think this is the first stop anyone considering DITA should make, it allows you to discover what it's like to author using DITA by working with the sample documents available at the site.
See also A Look at DITA and Help.