This weekend, a post by (my personal God) Stephen Abram identified some libraries doing some interesting things with Facebook Apps.
Specifically, I was taken with Ryerson U's new Facebook App for their library. I think this is genius--an app that exists in the sidebar, entirely outside of the Facebook profile page itself. This way, when the user wants their library tools, they simply click on their app to open it up. Install the Ryerson App on your Facebook profile and see what you think.
I think there is still great utility in widgets, and after we finish developing ours, I would like to see us move on to working on an App like this.