I use moinmoin wiki[1] on my own server, with a local copy on my laptop. Since it isa simple python app and stores everything in flat files it is easy to run and to sync.

Previously I've also used tiddlywiki[2], which can work locally in the browser or on a server, and also exists as a hosted service[3].

[1] https://moinmo.in/ [2] http://tiddlywiki.com/ [3] http://tiddlyspace.com/