bit.lySoftware by Base
Zimbra - Zimbra is trusted by over 500 million users to increase productivity with a complete set of collaboration tools while maintaining total control over security and privacy.
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.
iRedMail - A fully fledged, free email server solution, an open source project (GPL v2).
Zoho CRM - Omnichannel CRM for Businesses of all sizes
Roundcube - Web-based IMAP email client
Copper - Copper (formerly ProsperWorks) is easy-to-use customer relationship management for small businesses. Capture contacts and sales leads direct from Gmail with our simple CRM.