Pownce is a curious amalgam of Twitter and Pando. You can post comments, files, links, and events allowing one of your contacts, all of your contacts, or the whole Pownce world to view. Users can comment directly to specific posts. Unlike Twitter, you can have posts that are unlimited in size.

You can post using the Website interface. Pownce also provides a desktop tool that allows for posting. However, that is your only desktop option because Pownce has no public API. So unlike Twitter (which has a plethora of 3rd party applications) you get only what Pownce offers.