TripMate 850: i-Blue TripMate 850 Bluetooth GPS DataLogger with microSD Slot and LCD Screen (AGPS, 66 ch MTK2, 1GB MicroSD included)
I chose the TripMate 850 because it's one of the few dataloggers which has an LCD screen which can display the time.  This is very useful if you use the device for geotagging photos where it's essential that the datalogger time and camera time are synchronized.  Once the unit has acquired satellite lock I set the timezone on the device and then set the time on my camera to match.  This way I can ensure that when I merge the GPS track data with my camera images they never differ by more than 1 second.    Pro