Want to know if a Twitter account is run by a human or a bot? The Botometer hunts Twitter bots. A high @Botometer score suggests the account is probably automated. Accounts rated above 48% are flagged as potential bots—anything over 60% rates as a “likely” bot. It's a free product from Indiana University.
An alternative comes from the University of New Mexico. Like the Botometer, DeBot is a bot detection system for Twitter accounts. The information is archived so it can be searched.
Find more tools here.