There's a website called detexify that's sometimes helpful, and I also have used the wikibook on LaTeX a lot.
Ok. Looking at it, I don't see the point. It appears to search only for a symbol for which the LaTeX name contains the search term. So even if you know what the symbol is mathematically, it doesn't mean that the LaTeX is in anyway similar. And if you do know the name of the symbol, what are you doing on Detexify to start with