What are unity launcher widgets called and how do I configure/uninstall them?

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http://askubuntu.com – Ubuntu 12.10 has introduced among other things Unity launcher widgets that show, for example, unread Gmail message counts, twitter tweets, etc. While sites that support those widgets show notifications offering to install them, I can't seem to find how to configure and/or uninstall them. I'm particularly interested in Google mail desktop notification widget that seems to constantly turn my messaging indicator blue and the Last.fm widget that freezes my browser. Oh, and what are those widgets called? I can't seem to find the right name that will let me Google them. (HowTos)