Started using http://vimwiki.github.io/ after seeing it on HN. I've been quite happy, although it only supports plain text. The first-class support of images/multimedia here looks really nice.
I want to give vimwiki a try, but I need to be able to also use the wiki (read, search, navigate, write) from mobile. That's the only thing keeping me from trying it. I think I could store the files in Dropbox and at least read them from mobile.