I am not happy with any of the project management solutions out there. As a freelancer, I haven't found something that suits my workflow. What I need, is an application to aid my process from a to z: gather the requirements, weight the effort, helping me to get the job done and manage my invoices.
I've used many applications but these are the ones I gave most of my time.
Basecamp
Well, basecamp is the most famous solution for project management targeted at designers, developers and the like. But, the problem is that basecamp is better suited for small teams, not freelancers. My biggest peeve is the workflow; the separation between messages, to-dos, milestones makes me feel it is more about project communication than project management. Another problem is that the dashboard shows past activity—good for a team, useless for a lone wolf.
Freckle
Freckle is exceptionally good when it comes to time tracking. It also gained invoicing capabilities recently. But, I believe that evidence-based scheduling(EBS) is the best way to track your time. If you need an online app only to track time and invoice, freckle is the way.
The Hit List(mac app)
Basically, a to-do management application: THL beautifully manages your items, plus it also offers basic time tracking and estimation capabilities. Unfortunately the development has stagnated. I also used Things for several months but I found it lacked more advanced features.
Billings(mac app)
Billings handles your estimates and invoicing, it lacks an EBS-type system—otherwise, really good
FogBugz
At the core, it's an issue tracking solution. The first implementation of EBS, Fogbugz is not quite for freelancers: to big, to clumsy.
Besides the apps mentioned above, I also tried Backpack, Lighthouse, Harvest, Sifter, Sidejobtrack and many others.
The perfect blend is a mix between different features. Everything I need and nothing I don't plus a workflow tailored to freelancers. Maybe I have to build it myself.