Plaxo, Inc. keeps people connected by solving the common and frustrating problem of out-of-date contact information. Founded in July 2001, Plaxo provides a free service that securely updates and maintains the information in your address book. Plaxo is the universal digital assistant; available to you wherever and whenever you need it to keep you organized, on top of your life and in touch with those you care about.
Since its release in beta in November 2002, Plaxo has become widely popular, adding an average of 20,000 new users every day due to the service’s ease-of-use and simplicity.
They boast in having over 15mil users worldwide.
I personally like this service because it helps me keep uptodate contact information of Friends and business contacts (that's if they take the time to update their information).
to the most extent the information is uptodate.
I like using it to send people Holiday Cards, Birthday Cards, and thank you gifts in the mail.