I have nothing against APRS - it's just another gadget in the cockpit when you already have a gadget - it's called your transponder - and it provides a lot more data -- for nothing.
Go to my link for Flight Radar 24 - it's one of my favorite sites. You can track airplanes around Seattle - my location - or London, Tokyo, wherever. Easy. Most of the data is real time - some is delayed 5 minutes. The source are ADS-B squitter transmissions or FAA (and other) radars.
When I see strange airplanes, I check to see who they are and what they're about. In the morning, I can see the trans-Pacific flights descending into KSEA in advance, and watch them fly over from my deck.
If you have a Mode S transponder - the Hex code you entered during setup will automatically tell the world who you are - airplane type and tail number - and where you are. As I showed in my example picture, it will also show where you've been (and you can play it back the next day if you want.) And - it also shows your altitude, speed, vertical speed, and ground track. If you're "in the system" - either via a Flight Plan or just Flight Following, it will also show your origin and destination, ETA, and Squawk Code. If you have a Flight Number - mostly Air Carriers, but also - around here - Boeing test flights - it will show that too. You can track and follow an entire flight. And even watch it in 3D via Google Earth if you want. In many cases, you can even see a photo of the specific airplane.
You can do all that for free, and from anywhere in the world. If you have a Mode-S, gimme your tail number and I'll track you. Or - since I plan to go flying Mon and Tues, you can track me!
Flight Radar 24 - Never Leave Home Without It.
Bob Bogash
N737G
BTW - you can also listen in to the air traffic on the radio at many major airports, while following the flights on radar.
Since I live right on the water in a major shipping lane, I also can follow all this stuff for marine traffic - via a similar site:
http://www.marinetraffic.com/ais/default.aspx?level0=100#
And you can do this for rail traffic as well. Geez, I love this stuff!!!
If you check out my ham site - you'll see I can also do a lot of this tracking independently - on my own - since I also have my own radar - but that's a story for another day........
http://www.rbogash.com/ham.html