Aethera: www.thekompany.com/projects/aethera

CalDAV: ietfreport.isoc.org/idref/draft-dusseault-caldav

CAP Draft: ietfreport.isoc.org/all-ids/draft-ietf-calsch-cap-06.txt

Citadel: www.citadel.org

GroupDAV Draft: www.groupdav.org/draft-hess-groupdav-01.txt

Hula Server: hula-project.org/Hula_Server

Kolab2: www.kolab.org

OpenSync: www.freedesktop.org/Software/OpenSync

MultiSync: multisync.sourceforge.net

Noodle Project: noodle.yacoi.com

OpenGroupware: www.opengroupware.org

OPEN-XCHANGE: www.open-xchange.org

SOGo: sogo.opengroupware.org

SyncKolab: www.gargan.org/extensions/synckolab.html

SyncML: www.openmobilealliance.org/tech/affiliates/syncml/syncmlindex.html

UW Calendar: www.washington.edu/ucal