On a SharePoint website you can make lists to store information based on a list type. Some lists can be connected to Outlook, including contact lists, by using the Connect to Outlook action. The contact lists can be connected to Microsoft Outlook 2003 or 2007. If you connect to Outlook 2007, you can make changes to the contacts in Outlook and SharePoint. Outlook 2003 connected lists can be viewed in Outlook, but must be changed in SharePoint.

If you want more information how to connect SharePoint data with Outlook, see “How do I synchronize Microsoft Windows SharePoint Services 3.0 Contacts, Tasks or Calendar with Outlook 2007”.
Contacts are not send to your mobile
Contacts stored in your Outlook Address Book can be synchronized with your mobile device. Contact stored in an Microsoft Exchange Global Address List are also searchable on a mobile device. Although I expected a SharePoint list of contacts connected to Outlook 2007 to be synchronized with my mobile, that’s not working. I’ve searched through the configuration options, but found no option to sync the SharePoint contacts with my Windows Mobile 6 device. So keep in mind that SharePoint contact lists connected to Outlook are not synchronized with mobile devices out-of-the-box.
If someone made a solution for this, e.g. with Visual Studio Tools for Office, feel free to reply.