It is hard to count how many times I’ve scrolled through Scott Pakin’s The Comprehensive L^AT_EX Symbol List (pdf) looking for the LaTeX code for some obscure mathematical symbol.

That pdf document may no longer be the first place I turn.

Daniel Kirsch, a math student from Münster, Germany has created a very useful website for this purpose called Detexify²: LaTeX symbol classifier.

All you do is use your mouse to sketch the symbol that you want, and the website gives you a list of possible symbols that match your drawing (along with the LaTeX code and any font packages that you may need). It looks like it has a genetic algorithm running in the background, because it is being trained by your inputs (if do the courtesy of clicking on the symbol that you had in mind).

I found it remarkably accurate. Nice work!

Now they need to put this in as a TeXShop menu item.