Ask HN: Scrum/Agile tools for a distributed team?

Our 5-member team is distributed across several timezones (UK, East Coast & Central) and practice various aspects of 'Scrum' and 'Agile' to help us maintain and develop multiple projects for several internal customers. We currently use a mixture of Google Docs for our backlog and Trello for our iteration task board.

Unfortunately most of the tools out there make the assumption of team == project, so are there any tools that handle both the backlog and task board, and work well with multiple projects?