A slightly-larger-than-A7-sized pocket notebook that was 50p from Asda. The pages are quite small - 50-ish words/page. I had a bit of stuff backed up in my head to get down - not quite mindmapping, but some looping through thoughts about thoughts and some sentences being followed with a paragraph of caveats. I've just counted pages, and I filled a quarter of it, not a third - 19 pages out of 80, single side. I keep it in my jacket pocket with a pen, though I'm largely home for the next week or two so should keep it closer to hand. I don't actually do anything with the notes as yet; presumably one day I will type them up. Just getting it down helps clarify my thinking, though.
It has been noticed since the time immemorial that cognitive biases have a nasty tendency of being invisible to self (note the proverbial log in one's eye). Uncovering their own blind spot is probably the hardest task for an aspired rationalist. EY and others have devoted a number of posts to this issue (e.g. the How To Actually Change Your Mind sequence), and I am wondering if it is bearing fruit for the LW participants.
To this end, I suggest that people post what they think their current rationality blind spot they are struggling with is (not the usual sweet success stories of "overcoming bias"), and let others comment on whether they agree or not, given their impressions of the person here and possibly in real life. My guess is that most of us would miss the mark widely (it's called a blind spot for a reason). Needless to say, if you post, you should expect to get crockered. Also needless to say, if you disagree with a person pointing out your bias, odds are that you are the one who is wrong.
(Who, me, go first? Oh, I have no biases, at least none that I can see.)