I'm completely flummoxed by the level of discussion here in the comments to Unknowns's post. When I wrote a post on logic and most commentors confused truth and provability, that was understandable because not everyone can be expected to know mathematical logic. But here we see people who don't know how to sum or reorder infinite series, don't know what a uniform distribution is, and talk about "the 1/infinity kind of zero". This is a rude wakeup call. If we want to discuss issues like Bayesianism, quantum mechanics or decision theory, we need to take every chance to fill the gaps in our understanding of math.

Yeah, it might help to make a list of "math recommended for reading and posting on Less Wrong" Unfortunately, the entire set is likely large enough such that even many physics majors won't have all of it (lots of physics people don't take logic or model theory classes). At this point the list of math topics seems to include Lebesque integration, Godel's theorems and basic model theory, basics of continuous and discrete probability spaces, and a little bit of theoretical compsci ranging over a lot of topics (both computability theory and complexity theory seem relevant). Some of the QM posts also require a bit of linear algebra to actually grok well but I suspect that anyone who meets most of the rest of the list will have that already. Am I missing any topics?