We are always looking to add more WIDE digi sites to improve our system, and if you can help out by adding one to your favorite mountaintop, then please do so. We also have some WIDE digis at key locations which are at member's homes. These respond to the same settings as a remoted system, but help fill critical areas of coverage. You can add one of these to your home station by plugging it into the second serial port of your computer, or connect it to the TNC direct at the remoted WIDE digi on the mountain. APRS will then transmit temperature, wind speed and direction, and rainfall periodically across the network.
Some stations report barometric pressure as well.
The Agrello DFjr can be interfaced with a mobile or fixed site APRS station to report lines of bearing on any received signal of interest. This becomes fun when conducting fox hunts, illegal transmitters, or cable leaks. There are more fun things to do with APRS, and folks keep coming up with new applications. This should be a good start to getting you going. There are alot of us out there more than willing to help a newcomer in this fascinating aspect of amateur radio.