All the advice got before this is 'correct'...
the solarbotics one is pretty neat too!..
one is 'mine' (I home brew/etched it)..
the other is one by:
Anatools.com I believe..
(he used to even sell them on ebay if I recall)
**keep in mind this one has NO VOLTAGE REGULATOR **
so it can ONLY take a regulated 5v