I had been using MS Word to make all my IT documentation and saved in a structured folder but found it's hard to maintain and catch up. Oftenly, the steps to make a document made me reluctant to do so. I had tried a few Wiki tools but found it's hard for me to make a quite format rich documents in Wiki, besides, its non-standard HTML format makes it ever harder for me to do even a very simply instructions.
Finally, I tried and finalized to use telligent's new released Graffiti cms system as my IT document library. Its simplicity and flexibility totally meets almost all my needs. I can easily customize the layout and move content to or from wherever I want. It also works seamlessly with my favorite blogging publish tool, Windows Live Writer. Whenever I want to document something, I can simply fire up my live writer, write something down, pick up which category should belong to, and publish it right after I finish it. Yes, comparing to Wiki, it lacks of the version tracking but this is not what I am concerned the most. However, if the revision control weights pretty well in your list, you should be considering Wiki instead.