Detexify2 – LaTeX Symbol Classifier
http://detexify.kirelabs.org/classify.html

Anyone who works with LaTeX knows how time-consuming it can be to find a symbol in symbols-a4.pdf that you just can’t memorize. Detexify is an attempt to simplify this search. Just draw the symbol you are looking for into the square area look what happens! This has been added to the tools section of Research Resources Subject Tracer™ Information Blog.