Basecamp is a web-based tool that lets you manage and track projects (or simply ideas) and quickly create client/project extranets. Over 1,000,000 people signed up.
LiquidPlanner is online project management software that uses an innovative scheduling engine to help teams with project planning, resource scheduling, and collaboration.
OpenProj is a free, open source project management solution. OpenProj is a complete replacement of Microsoft Project, and other commercial project solutions.