Hello, my name is Mike, and I'm a nerd.
Once I found out that the D90 has the ability to record GPS position data with the pictures (geotagging) I was on a mission. Nikon sells a GPS unit that mounts on the flash shoe and looks really nice, but, I already have a Garmin GPSMAP 60CSx that should work, right? I mean why buy another piece of hardware when I should be able to hook the two pieces I already have together and accomplish the same thing, right? I mean I'm an engineering guy, so all I should need is a couple of cables with the right connectors and I should be able to coerce the camera and the GPS into talking to each other.
Well just a bit of Googlage revealed other folk with the same idea, and some quality time with my web browser yielded acompany in hong kong that sells two pieces of cabling that provide the required interconnection. One EBay transaction later and viola', instant GPS position data being recorded with the pictures. Sweet!
Go ahead and say it ... "why do you need GPS position data for your pictures?, I mean you're taking the picture so you already know where you are, right?" I could answer that "it's for geotagging", but the truth is it's just because I can. Yep, I'm a nerd. Now I need a mounting bracket for my GPS so that I can hang it on the tripod while I'm taking pictures!
If you're interested, here's a link to the web where I bought the cable: http://www.pc-mobile.net/nikongps-cable.htm