"Yesterday I sent out mail to a few dozen beta testers to let them know that we had started the beta of our implementation of the MetaWeblog API for MSN Spaces. For the uninitiated, the MetaWeblog API will enable you to create, update and delete posts within the blog on a space. This means that you'll be able to use tools like Blogjet and W.Bloggar to manage the blog on your space."
I like this: "RSS/Atom readers that have a "Blog This" feature can be used to post directly to your space."
If you want a try, ping Dare - he's looking for more beta testers.