This document discusses different types of online political party memberships and examines evidence about their emergence. It identifies several types of online members including trial members, lite members, cyber activists, sustainers, social network friends, and news audiences. Studies of online party membership show that websites are used mostly for information rather than discussion. Email is a powerful mobilization tool for existing members. Parties should offer tools for members to get involved and integrate organizational data to activate inactive members on key issues. Successful online organizing blends information, fundraising, and mobilization.