Tricki
The wikipedia-like repository for mathematical “tricks” has now gone live. Their mission statement:
The main body of the Tricki will be a (large, if all goes according to plan) collection of articles about methods for solving mathematical problems. These will be everything from very general problem-solving tips such as, тАЬIf you canтАЩt solve the problem, then try to invent an easier problem that sheds light on it,тАЭ to much more specific advice such as, тАЬIf you want to solve a linear differential equation, you can convert it into a polynomial equation by taking the Fourier transform.тАЭ