I am using detexify for quite some time now, saved me time and nerves on countless occassions. I hated it to dig out symbol declerations on and on again.
Nice!
There is also free Android and Iphone versions available in the market/App store.
For me, it failed to identify either alpha or beta. Not that I care, since I can type the symbols faster than I can take my fingers off the keyboard to mess around with a pointing device.
I managed to draw my 'alpha' backwards (whups) and it still worked OK for me. Maybe it's just a penmanship-related quirk?
I drew a beta using the mouse with my wrong hand, and it worked ok.
I got all excited and then it interpreted my volume integral (∰) as a left angle bracket. :(