Design for a single chip frequency counter using PIC12F675. It is possible to use the internal RC oscillator, instead of the crystal but the accuracy suffers.
http://www.dougrice.plus.com/hp/freqCounter/freqCounter.html
circuit to to measure a frequency much higher than the internal clock frequency of the microcontroller
http://www.edn.com/archives/1998/030298/05di.htm
with an AVR 2313
http://www.myplace.nu/avr/countermeasures/index.htm
Using a 4511, a specialized decoder IC, learn how to drive a 7-segment display. The article explains the technique for counting from zero to nine.
http://www.nutchip.com/progetti/counter_en.htm
measure frequency well into the microwave range
http://www.northcountryradio.com/Articles/counter.htm
http://www.qsl.net/vu2upx/Projects/frequency_cnt.htm
will take a 0.1 - 3 GHz signal and divide it by 1000
http://www.qsl.net/n9zia/wireless/appendixF.html#13
http://www.4qdtec.com/aoc.html