A really good list of Twitter resources

TwitterLocal

Twitter Tools from typepadhacks.org

Inc. Magazine's March 2008 interview with Evan Williams, Twitter

Twitter Etiquette

Twitterholic

Quotably - follow the conversation

Twitter In Plain English by CommonCraft

Getting Started...

Hashtags

Terraminds: A Twitter Search

Twitter Packs: Who to follow

Twitter Clients

Twitter Badges

Clive Thompson on How Twitter Creates a Social Sixth Sense | WIRED MAGAZINE: ISSUE 15.07