HubSpot CRM - Free CRM software for small businesses.
Freshservice - Freshservice: the one-stop cloud solution for all your IT management needs.
Less Annoying CRM - A simple customer relationship manager made just for small businesses. Manage contact info, track leads, and never miss a follow-up.
Freshdesk - Freshdesk is a cloud-based customer support software that lets you support customers through traditional channels like phone and email, social channels like Facebook and Twitter, and your own branded community
Keap - Grow Sales. Save Time. Get Organized.
Zendesk - Zendesk is a beautiful, lightweight help-desk solution.