Ask HN: Collaborative mindmap software

Looking for suggestions for a mindmap software package that supports collaborative editing. My team is looking to build a 'team mindmap' that we'd all like to be able to edit. Free or paid is OK. We already are using MindMaple Pro which is great for creating single-user mindmaps, but it doesn't have a collaborative editing mode. Note that I'd prefer to have a hosted solution (in-house or out) that we can all access as opposed to a solution that requires us to checkin/out a shared file.

Thanks!