I have been using mediawiki and Drupal to make notes for things that have learnt or good stuffs on the web that I had stumpled upon. However, I have to admit that my knowledge about them is really elementary.
Since I was on leave for these 2 days to take care of Young (he is having fever), I browsed through their documentation in more details. Mediawiki is still more flexible. I did not use it much earlier because it was too slow (not sure that was because of my hosting service or the old version of mediawiki). Its speed is now more acceptable.