Twitter Vigilance

Trendistic: a real-time keyword tool

Twit(url)y: a URL popularity tracker

Tweet Back-up: not analytics per se but potentially handy

http://www.gottaquirk.com/2009/07/16/twitter-measurement-tools/

http://www.bernaisesource.com/blog/2009/06/a-roundup-of-twitter-tracking-tools/

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