There's a new Google gadget called sidewiki. To be able to use it, you need to equip your browser with the latest version of the Google Toolbar. Click the banner on the left to visit a website that invites you to obtain and install this Google Toolbar.
For the moment, I'm playing around with this new gadget, to get a feeling for its behavior. My first impression leads me to see this new Google thing as an extremely potent device, since you can apparently attach your humble "side stuff" to any website you visit. But I haven't yet figured out how they plan to control the risk of pollution, spam, etc. We'll see. Normally, you should be able to test this gadget upon the present blog. So, go at it!