Started mobile APRS with a  Tiny Track II from http://www.byonics.com this gave me a good grounding in APRS, I have since moved on to a Kenwood TH-D7E,D700 by Kenwood and I am currently using the fantastic new Kenwood TM-D710E.

APRS is up and running from the shack as MB7UNR 24x7
Or if you want a UK map of currently active stations click here :-

Software can be downloaded from http://www.ui-view.com to enable you to track APRS stations.
No need for a TNC you can use a soundcard.
An excellent site and guide  http://www.qsl.net/soundcardpacket