Extending Office Live has recently been made easier through the introduction of this web service which provides specific API access to core parts of the platform.  There are also many Sharepoint Services APIs to play with via web services but some of these are blocked because of how Office Live works atop the platform.

Chris is currently looking for feedback on what's missing from the current API and wants you to let him know if you think of anything or come across any limitations should you find them.  If you want to make changes to the product then get in touch with him - simple as that!