We use Salesforce for CRM, so we implemented Financial Force PSA. This has been an excellent solution for us, but it definitely requires a lot of customization to represent your business processes (like any holistic solution would).
I have found that agency and video production is usually based around a sub-set of the larger team getting together for a duration of an event or project.
To facilitate the changing team members as well as shifting priorities in these environments a tool such as Trello works well:
You might be interested in trying out trello.com. We use the higher end paid version and have been really happy with it. It's very visual and customizable. I've seen it in use at an agency of 40+ employees as well as smaller 5-6 person production houses and it seams to do really well.
We've created http://taskware.do which is kanban-based like Trello, we are an agency that dealt with many other apps that didn't quite cut it.
Check it out, I'd be happy to give you a free membership.