Zoho ContactManager!

Google Contacts is Google's contact management tool that is available in its free email service Gmail, as a standalone service, and as a part of Google's business-oriented suite of web apps Google Apps.

FullContact's apps let you keep all your contacts in one place, automatically up-to-date. This social contact management software automatically cleans your contacts, enriches them with social profile data, and continually syncs them across devices with all your contact sources. You can also merge duplicate contacts, scan business cards, capture email signatures, and more.

Alternion is a social hub and communication center that enables you to combine and manage all your social web and email in one place.

fruux is a free service that takes care of your contacts, calendars and more so you don't have to. Never manually copy contacts and calenders between your devices again!

With Memotoo, sync all you want !

Pobuca - where teams share contacts

Kylook synchronizes your address book with Outlook, Gmail, Yahoo, Linkedin, iPhone/iPad, Android, Windows mobile, Blackberry. It removes duplicates, allows fine grained access rights, does automatic backup and a lot more. Free up to 600 contacts.

GlipMe is the living address book, that enhances personal and business contacts. An online address book that is a powerful resource for your business and your personal life.It's a Web app, integrated with Gmail, Office 365, LinkedIn, Twitter, Asterisk, ecc. and doesn't require a dedicate App to synchronize any smartphone.

Open Contacts is an advanced address book program for managing contact info of individuals and organizations with relationships. Distributed as freeware, the program was designed for people who need more beyond ordinary address book programs in order to improve dynamic interactions with contacts. In addition, with SyncML for Open Contacts, you may synchronize contact info with smart phone, PDA and Web address books etc.