One of the neatest features in the discontinued-but-alive Google Wave was its collection of gadgets and extensions. Many of those gadgets live on in Google's new Shared Spaces, where you can invite others to contribute, vote and collaborate on the web.
More than 50 Wave gadgets have made the transition to Shared Spaces, with the collection broken up into rough categories. Click on a gadget, and you'll quickly create a URL you can easily share over IM, email, chat windows or wherever. Check out Google's slideshow explanation of how Shared Spaces works: