I found out about RebelMouse because I went to hear Cory Doctorow talk. He mentioned Peter Black, who I started following on twitter, and he tweeted about his use of RebelMouse.
At this stage you have to ask for an invite, which I did for a work related social media channel and for myself at the same time. My invite came through in less than 48 hours and the work related one still hasn't. I have no idea of the criteria. I am hoping the other invite comes through because it will have some interesting potential for collaboration.
I am enjoying it. You have to remember that it is not showing all of your tweets - just the ones with some kind of visual element, so it works well for tweeted websites and images, and not text only. Yesterday I was tweeting all day at a conference, and less than a dozen of the tweets showed up on RebelMouse. I realise that this is not necessarily a problem.
I like RebelMouse as it provides a different way of looking at tweets.
Go to RebelMouse and ask for your invite - and see what you think about it.