1. What are the tiny ‘D’s in the bars on the satellite page?
It means your unit is receiving WAAS signal corrections for those satellites.
2. How can I use my Garmin GPSMap 60CSx with a program that expects an NMEA datastream such as Microsoft Streets & Trips?
On products that use a serial port, you can use an aftermarket serial cable and attach it, but most users will find more joy in using USB with Garmin Spanner or GPSGate to create virtual COM ports that programs like Streets & Trips or Delorme can use.
GPSGate is a more flexible program. Spanner does pretty much one thing – converting Garmin PVT to NMEA – but it does it for free.
3. How can I take a screen dump or capture the image on my Garmin GPSMap 60CSx?
Garmin xImage will capture the screen of your GPS and save it to disk.
For more FAQ please visit http://www.gpsfaqs.org