As we work on client-based projects as well as our own suite of software, we have some unique needs. In a sense, we run more than one business - we make websites with content management systems, and we also make software which we deploy content management systems with. To that end, Basecamp has been working really well for our client-based projects.
We have found, however, that our requirements for working on our own software are slightly different. More specifically, we are finding that we need to prioritize work, categorize it based on status, pass off tasks to each other, and keep the ball rolling on specific pieces of functionality without having to "manage the management" too much.
We like the functionality found in Mantis, we like the interface of Lighthouse - is there a piece of software online that combines the best of both these worlds? Mantis is lacking a designer-friendly look and feel, while Lighthouse is lacking some of the key features that Mantis picks up the ball on, such as status (critical, non-critical, feedback required, etc).