Just FYI for those of you who aren't keeping up with what's happening in the ADS-B world.   Here is a map of coverage in the SE part of the US that just took effect this week.  

https://www.faasafety.gov/files/notices/2010/Aug/ADS-B_FINAL_Jacksonville.pdf

If you have an ADS-B UAT, you can receive TIS-B (traffic) and FIS-B (weather). and don't need a mode S transponder.  If you only have a mode S transponder then you can receive TIS-B (but not weather)

This service is free.  All you need is the UAT and a compatible display.  A UAT is a transceiver that operates on 978Mhz and transmits your position, altitude, aircraft callsign to ATC and other UAT equipped airplanes.   UAT's also include a built in WAAS GPS receiver, so when you install one, you will have to install two antennas.  One GPS and one 978Mhz antenna (basically another transponder antenna).  

Ron