I had intended using Basecamp for project management and testing co-ordination as it's a platform I'm familiar with. They seem, however, to have dispensed with their free tier and, as I'm trying to keep costs at a minimum, I had to look for an alternative. I opted to try Teamwork.com for the project. It seems to do a lot of things well and, critically, has a free plan that supports 2x projects and unlimited users. I'm in the process of sending out invites to those who offered to help with testing so we can have a central point of communications.