I just published my mbed driver for the Maxbotix sonar range finders.
Unlike the existing drivers for these modules, I am using the pulse width output from the module to read the range with lower latency, higher accuracy and lighter CPU load on the mbed, and without using up an analog input. The driver does take two interrupts per sample but this is much lighter load than the interrupt per character of serial input or the resource consumption from using an analog input.