The design and usability gurus at 37 Signals have announced the availability of Basecamp, a hosted, Web-based service that helps you manage projects and quickly create client/project extranets. “It lets you and your clients (or just you and your own internal team) keep your conversations, ideas, schedules, to-do lists, and more in one password-protected central location,” explains the company. “And unlike most project management products, Basecamp is a breeze to use.” 37 Signals said that the product, which also sports iCal integration, was built and tested exclusively on Macs.