Most people these days keep their contacts stored somewhere that they're frequently used, such as on a cell phone or in an e-mail client. If you prefer a standalone program for this task, My Agenda is a no-frills option that lets you record contact information and even dial numbers automatically.
My Agenda's interface consists of a small rectangular box with a handful of buttons. Contact names are displayed in a scrollable list, organized alphabetically by first name; since there aren't separate fields for first and last name, you can easily change this by simply creating your contacts with their last names listed first. The program also has a search option that lets you search by name, address, or other fields. For each contact, you can record one address; a phone, fax, and mobile number; an e-mail address; a birth date; and notes. The program can display all of the birthdays occurring in a given month, which is a nice touch. Perhaps the most useful thing about My Agenda is its ability to automatically dial phone numbers; people who have never used such a feature, though, will have to seek instructions elsewhere, as My Agenda offers nothing in the way of information about how to configure it. This is the only potentially confusing aspect of My Agenda, so overall, the lack of documentation isn't a problem. My Agenda is a pretty bare-bones solution to managing contact information, but it's not a bad choice if that's your style.
My Agenda comes as a ZIP file and is accessible after extraction with no need for installation.