eMule - eMule is a free peer-to-peer file sharing application for Microsoft Windows.
Baïkal - Cal and CardDAV server
Soulseek - Soulseek® is a unique ad-free, spyware free, and just plain free file sharing application.
Radicale - The Radicale Project is a complete CalDAV (calendar) and CardDAV (contact) server solution.
Shareaza - Shareaza is the most luxurious and sophisticated file sharing system you'll find.
DAViCal - DAViCal is a server for calendar sharing.