Overnight I've been thinking about Google's new Wave dealy.
I can see a Wave server being woven into a Sakai deployment to facilitate ad hoc and classroom projects, with the Wave robots tracking participation and in simple cases grading. Cross institution wave components can federate.
Wave client thingy is written in GWT, stitched together with Guice and GIN.
My first concern is for the amount of bandwidth this can soak up. Each keystroke - yes - is a callback up to the server. gulp. I haven't plowed through the protocol but I think it's XMPP ( Jabber spawn ) with extensions.
Since I'm between projects... hmm... sniff. hell I better do public write up of the last one!
Other quick hits:
Project management - Lombardi's Blueprint is a very impressive hunk of engineering. Their GWT implementation is beautiful. Might be of a low-ritual scale Sakai implementors could find useful.
Instant slideshows - Animoto. Upload your still images and a clicktrack (ok they said music) and it will auto keyframe a set of configurable transitions based on the clicktrack. nice stuff.