What are the qualities of a good software development team leader?

Being a leader, the first and foremost qualities you need are all related to working with people.

A good team lead is someone who knows their team - knows their strengths and weaknesses, who coaches them when needed, encourages and motivates them to continue in troubling times, who listens, mitigates, resolves problems - who gets the team focused and eager in meeting their project milestones - doing their work, enjoying it and having fun.

Is diplomatic, resolves issues that arise during product development, who can easily communicate to management, customers, and his/her team members, treating all of these people with the utmost respect.

At the end of the day, if people in your department all desire to have you as their lead, and hope that the next project they're on is one of yours, then you have done your job.

Of course, in most cases, being technically proficient at the technology you're using to develop your product, and having strong development experience, knowing design patterns, (etc) ability to effectively peer review code and approve design documents, functional requirements, technical specs, will all help and is generally a requirement to being an effective team lead.

Knowledge of how to program different type of computers, solid people leader skills, and curosity about most of the world around her or him.