Zempt is a MovableType posting client. I’ve downloaded it (in fact, I’m posting this from it), and although it’s only in a 0.2 release it looks great. It supports a lot of specific MovableType features like multiple categories, text formatting plugins, and pings.

I couldn’t find a way to edit old posts, but it’s probably coming in the next version. Once Zempt supports the full MovableType XML-RPC API, it will possibly be a much better choice for posting to a MovableType blog than w.bloggar.