Professional Development for anyone associated with education should include updating http://www.wikipedia.org/. It'll be easy to add to your list of personal goals. It'll be a little tougher to add it to your co-workers' list of goals. It'll be even harder to get credit noted as part of promotion and tenure, but it *should* happen.
The reasons are many. Fill in your own. Meanwhile, start with updating a private wiki if you'd like, but make it a priority to edit wikipedia.org. Blogs may be nice because everyone has something to say, but wikipedia is better because everyone has something to add!
The best part if the deal is that your additions will then be reviewed and made better by
The challenge is to make it happen.