I saw this go by on another APRS mailing list (UI-View) back on 8/8/2008:
Here are those common defaults:
-0 Home Station, Home Station running IGate.
-1 Digipeater, Home Station running a Relay Digi, Wx Digipeater
-2 Digipeater [#2 or] on 70CM
-3 Digipeater [#3]
-4 HF to VHF Gateway
-5 IGate (Not home station)
-6 is for Operations via Satellite
-7 Kenwood D7 HH
-8 is for boats, sailboats and ships (maybe 802.11 in the future)
-9 is for Mobiles
-10 is for operation via The internet only
-11 is for APRStouch-tone users (and the occasional Balloons)
-12 Portable Units such as Laptops, Camp Sites etc.
-14 is for Truckers
-15 is for HF
I've chosen -12 for my APRSISCE as it is definitely portable and may someday actually go via RF. -10 seems more for non-mobile Internet clients like WinLink and UI-View.
Lynn (D) - KJ4ERJ - Author of APRSISCE for Windows Mobile
PS. I'm posting this here so I can quit trying to remember where it was that I saw it before!