Mailstrom is an amazingly powerful, deceptively simple email tool that helps you clean out your inbox and keep it clean. It analyzes any IMAP inbox (such as Gmail) and organizes it for quick bulk actions that help you reach Inbox Zero and stay there. At http://mailstrom.co
Shortmail.com makes email a simpler, happier experience by limiting the size of emails and organizing around people, not piles of messages. The iPhone app gives email the immediacy of chat.
Replyz.com turns Twitter into a useful Q&A platform, helping people start and join conversations based on shared interests.