OS X Lion Server
Lion Server includes AFP, SMB and WebDAV support, a built-in email server with SSL, Push notifications and junk mail filtering, iCal server, Address Book Server, iChat Server, Wiki Server, Podcasting publishing support, TIme Machine server support, Xsan, and more. It also offers step-by-step walk-throughs for setting up server features, and includes remote and local administration support.
OS X Lion Server is priced at US$49.99 and requires OS X Lion. It is available for download at Apple’s Mac App Store.