General GPS project notes
From Wildsong
Garmin
Trimble
Lassen
Lassen SQ
Serial TTY to RS232
Serial TTY to Bluetooth
Serial TTY to USB
PIC datalogger
Power supply
High efficiency switching voltage regulators National LM2597 3.3 and 5.0 "Simple Switcher" 8-DIP $3.78 Digikey
Requires 1N5817 Schottky diode and 100 uH inductor (M9799-ND) and the usual handful of caps.
Backup / standby power
Button cell batteries - CR2032