###Update April 30th, 2012
I manually ported this entry over from Posterous.
Assistly was acquired by Salesforce and rebranded as Desk.com.
I know that our own plan at Goodbits for Tender was grandfathered, and I suspect many of the other pricing plans have changed as well.
Further update: My answer today is Intercom - read the longer post on the Full Stack tools section »