There have been many 3rd party paid Wikipedia apps available for the BlackBerry PlayBook. However, Wikimedia has finally brought the official Wikipedia app to the PlayBook. The Wikipedia app has features like: Search articles nearby, Open articles in browser, and Read article in a different language.
The Wikipedia app is also open source. If you are a developer and good at JS/HTML5, you can contribute at https://github.com/wikimedia/WikipediaMobile