Facebook beta app for webOS gets Places support
To check in, simply tap the menu button in the app's top-right corner and then tap the Places icon. Nearby locations will be displayed, and you can then tap Check In to post your location to Facebook.
Places support is only available in the beta app right now, so here's hoping the new version gets rolled to all webOS Facebook users soon. It's a big improvement and has a lot of nice additional functionality.