Derek Punsalan of 5thirtyOne has posted a great write-up on the differences and advantages in three online project management and collaboration tools. The article lays out the options for Basecamp, activeCollab, and Goplan.
My project list is not quite big enough yet to pay for a project manager service. However, I do have enough projects (between home and my day job) that Basecamp’s free plan was not enough. So, activeCollab was the best solution for my project management. I installed and stated using it about 3 weeks ago. Without the current need to collaborate with other companies / teams activeCollab works for me.

