I contribute to the following wikis:

• ArchWiki
• Cosmologia (solo user)
• Game Making Tools Wiki
• MobyGames
• Select Button Wiki (No userpages)
• Sword of Moonlight Wiki
• The Tilde.town Wiki (No userpages)
• Wikia
• Wikipedia

• This one!

I tend to write my notes in Markdown (may just switch to org-mode at some point?), so being able to easily convert from that syntax to something I can plonk into a wiki is very useful! You can even grab HTML files and stuff straight from the WWW.

MD to Doku

pandoc [inputfile.md] -f markdown -t dokuwiki -o [outputfile]