Measuring the spin of a single electron

The spin of a single electron has been measured since the very first moment when the people understood that every electron possesses a spin. A Stern-Gerlach experiment - a magnetic field - is enough to measure the spin:

http://en.wikipedia.org/wiki/Stern-Gerlach_experiment

First you need to be assured of a source of single electrons. A good one is from spontaneous decay called conversion electrons. Then you set up a Stern Gerlach magnet setup. The problem is that one would need to cancel out the transverse Lorentz force, and this can be done with a transverse uniform electric field to cancel it out. Then use solid state electron detectors to see the deflected electron event counts.