Our Man in Ballmer suggests: use a tuning fork to tune middle C; then tune C one octave above and one below, then tune E, G, and B-flat from there etc.

This will produce a tuning that sounds great in C, in fact even better than the normal tuning in which you tune each note individually to a standard reference. As you depart from the key of C around the circle of fifths (C-G-D-A-E-B-F#/Gb-Db-Ab-Eb-Bb-F-C) the tuning will get worse and worse until you hit F#/Gb at which point it will start to get better until you get back around to C. If you are interested in this tuning see http://www.dnai.com/~jinetwk/.