NeverBounce - Real-time email verification and cleaning to ensure emails never bounce.
HEY - Email at its best, new from Basecamp.
Email List Verify - The Fastest Way to Improve Email List Deliverability and ROI
InstAddr - Disposable email address application.
ZeroBounce - Removes invalid emails from your list to prevent email bounces from ruining your deliverability.
Horde - Horde Groupware is a free, enterprise ready, browser based collaboration suite.