Well I can't promise these are in order of release, but here goes...
Dolby Pro Logic 2, BIG difference over PL 1, mainly 2 discreet surround channels instead of just 1 being fed through 2 speakers giving a 5.1 effect to music and movies. On newer receivers/amps there PL 2x which transforms 5.1 & 6.1 into 7.1 surround. There are music, movie and game modes to this and is much more customiseable than PL 1.
Dolby Digital and DD EX...DD is the standard surround format used for DVD, it gives you 5.1 channels of discrete surround versus the encoded/matrixed dolby surround. EX has a 6th rear center channel matrixed into the rear channels to give you 6.1 surround.
DTS/DTS-ES/DTS NEO:6 DTS is 5.1 like DD but not as widely used on DVD, it is less compressed, which means it sounds better (IMO mid to high range are clearer) DTS-ES is like DD EX, but unlike EX its 6th rear channel is discrete. NEO:6 is much like pro logic 2, this surround mode gives you 6.1 channels from any 2 channel source. You can choose from music and movie mode.
There are also some THX and THX EX modes which I don't know too much about, from what I hear it takes DD or DTS and adjusts the sound to make it sound exactly as the makers of the movie intended it to sound.
You can get more in depth details on
www.dolby.com www.dts.com and
www.thx.com
Hope this clears things up
