FeelLikeWritingSomething on wiki? Don't!
"Feeling like contributing" is often a long way from having something constructive to say.
If you often feel like writing but don't have something that needs saying, start a journal (the personal kind). A journal is a very effective catharsis and a great way to polish your writing skills for the times you do need to write something eloquently. It's one of the many WonderfulBenefitsOfJournals. If you really want to write on wiki for the sake of writing, using your HomePage is a reasonable compromise.
This is also true in meetings. Sometimes, when there's a sufficient number of people in a meeting, you feel the urge to say something - anything. Unfortunately, those are the times when one makes the most inane comments. Instead, listen actively; take some notes. A closed mouth gathers no foot.