I did search thinling there was a prior thread mentioning ACARS, but cant seem to find it at this time.
So heres a new one on my recent playing around.
Ive been messing around ever since Police went *whistle* digital here with other aspects. One of them being ACARS decoding. And now ADS-B. Pointless data, but one of those 'cause I can!' hobbies.
ACARS is a short message system from a centre console in aircraft to/from ground crews. With data regarding flight plans/weather/general comms/GPS co-ords.
Ive been dumping this data into a SQL database for display in a nice PHP generated table (will an example later) which translates Registration/AC type etc.
The more recent on-the-cheap purchase was to get a microADSB unit, to decode ADSB radar signals.
This is a different mode of plane-plane radar that more or less says 'here I am, dont hit me' negating the need for ground controllers between continents.
This method has a GPS location within each 'blip' and software is able to display this graphically. There are 3 stations in NZ, NZAA, NZCH (off atm) and NZPN all inputting to http://www.flightradar24.com for quite a bit of coverage over NZ, but zoom out to see the traffic over AU/Europe :)
Another good NZ based resourse is http://www.nzradar.com Mike has been helpfull to point me in the direction when working with the SQL/PHP stuff and also has quite a few logs to browse.
If anyone else is interested in getting into it. Sing out.

https://cdn.geekzone.co.nz/imagessubs/15741f76a297eb91095c15e89c7e964e.jpg
This shows Emirates comming in from around 10,000ft, then a local Airbus beating it to the ILS path