I haven't (yet) found an ideal solution, but I have at least found two different ways to update my Facebook status without ever having to directly launch Facebook.
- I installed the Twitter application on Facebook, by following these instructions. Now each time I update my twitter status I can have the status update automatically propogate to Facebook by simply appending #fc at the end of the status message
- I linked my Plaxo account to my Facebook account by logging into Plaxo and clicking on "edit my profile", selecting "websites" tab and then clicking on the Facebook icon and entering my credentials. Now any time I update my Plaxo status it automatically generates a Facebook status update with the same text and visa-versa.
[Update 26/May] - It turns out that the Plaxo/Facebook connection is bi-directional and not one way as I originally stated (the Facebook to Plaxo update just happened very slowly so I thought it wasn't working)
[Update 4.June] - Robi Brummer pointed me to ping.fm which is a great site for updating several sites at once. The list of services that work with ping.fm is truly amazing