Onesheet CRM - The Simple CRM for Google Sheets
Freshsales CRM - A full-fledged CRM for high-velocity sales teams.
Followup.cc - FollowUp for email is a lightweight productivity suite that keeps your conversations and tasks from slipping through the cracks. Set perfectly timed reminders that arrive at the top of your inbox, right when you need them.
Crmble - Easy peasy crm for Trello
Pipedrive - Sales pipeline software that gets you organized. Helps you focus on the right deals, so easy to use that salespeople just love it. Great for small teams.
HubSpot CRM - Free CRM software for small businesses.