The best remote team collaboration and brainstorming tool

I use InVision Freehand to run online workshop sessions with internal team members and clients. This is an excellent real-time collaboration tool that replaces what we used to do in-person with paper post-its. We use it as a brainstorming tool that lets everyone create cards and then prioritizes/organizes ideas later. We also use it as a way of capturing meeting notes. As you take notes, you can easily move around cards to organize thoughts and create a simple diagram while someone shares their ideas. Best of all, you can save all your Freehand sessions, whereas I can't easily keep all physical post-its in person.