Trello is definitely the best free tool available. We use it to track our sprints, app development, marketing strategies, sales pipeline, and nearly any other multi-stage process that requires micro visibility. It’s beautifully simple and incredibly powerful.
Cushion is simple and addictive forecasting app designed specifically for freelancers. We use it daily to track our own sales pipeline, project load, overall financial goals. It’s currently in beta, but already worth the price of admission.
Basecamp is practically the default project management tool for digital agencies. It’s simple to onboard and works great if you’re looking for a straightforward client communication tool. Wish they’d introduce a clear kanban flow with better messaging formatting, though. Ironically if you’re looking for the best version, Basecamp2 might be a better choice while they’re still offering it. Fewer silos in the functionality.