If you want your own wiki that you are the admin of, you can get it through a few sites.
List of them hereI've had personal experience with
Wet Paint and
PB Works. I really liked PBWorks.
On one of the sites I host I used a wiki engine called
Dokuwiki. I really liked that engine. I don't think any free sites similar to wikia, PBWorks, wetpaint, etc. use this engine, however.
But, I did find a
guide on how to set up dokuwiki on free hosting if you like the look/feel of that specific engine.
For an example of what dokuwiki looks like, go
here.