Here is a recent DIY Physics article on eBay Rb oscillators for anyone interested. It's probably more basic level (read my level) than many/most on this list. But it may be interesting or useful to others here. http://www.diyphysics.com/2012/02/14/d-i-y-10-mhz-atomic-clock-frequency-standard-using-surplus-rubidium-oscillator/ -Mike-