Some thing that I've known for a while is that Google Buzz, Google Reader and any good RSS reader supports iframes, it's how I figured out how to embed a Google Wave within a Buzz post.
I've always thought it'd make a cool unofficial application platform in Google Buzz if the trick was mixed with Google Gadgets and Open Social but I never knew if it would work or not, mainly because I haven't tried, so here's my first attempt.
(To see the social gadget test in action you must have people in your friends list in your Google contacts)
Of course this is all useless as Buzz users are Gmail users and if they wanted to run Apps/Games they could just use the feature in Gmail Labs, especially since it supports social gadgets and a canvas mode.
Maybe Google will integrate Buzz with the Gadgets feature in the future with these "GoogleMe" rumors going around.