What exactly are you looking for? We use Hipmob (we also ARE Hipmob.com) for live chat for our apps and our website, and Desk.com to handle email traffic and knowledgebase. We've also used Zendesk to handle email traffic in the past, as well as Olark to handle live chat for websites, and both work pretty well. Have heard of folks using Intercom.io for semi-automated in-app messaging, to good results.