Movies:
Aphabetical (by original title) except for some "special" categories: e.a.
Actors/Directors (sorted by actor/director then by year):
Hitchcock
Spielberg
Eastwood
Welles
Kurosawa
Jackie Chan
Takeshi Kitano
Scorsese

Genre/Country/Studio (sorted by genre ou country or Studio, then year)
Universal Monster Movies
Disney Animation (by year)
Pixar Animation (by year)

TV:
Alphabetical

Music:
Alpabetical (by artist)

Other (Sports/Docs/...)
No idea... 

I gave it plenty of thought before i entered into a "sorting" phase with my DVDs.  Alphabetical was out simply because it was too labor intensive, as I add new DVDs each week.  Likewise, sorting by genre was just as impractical, there are too many movies that seem to cross genre barriers too easily to be defined as a certain genre first.

  And so my search began, for a program that would list my DVDs and catalog them for me, in pretty much any way I wish, and VOILA    here I am!!

  I keep my DVDs (in their cases) in clear plastic boxes, sealded away from most of lifes little "floaties" and smoke trails, each box contains on average 16 DVDs, simply adding a box number to the list as I enter each new arrival, I know exactly where to find any title without having to worry. DP3 is my instant resource, and printing out a title list when i go shopping is a great advantage in being able to see at a glance if I have it or not,  and with well over 2000 DVDs I need all the help I can get.

  Oddly enough I am just now getting this pc whipped into shape again after a particularly nasty breakdown and will be adding all my titles again,  but I can wait until the cuecat arrives...

I've got shelves that fit perfect if you only put Keep Cases, Steelbooks and Super Jewels. That's why I put all boxsets and Digipacks and Customs into a seperate shelf.

The Keep Case shelves are sorted by decade and within a decade alphabetically (by original title or international title for asian movies).

My Disney movies go seperately too, most of them are part of the "Special Collection", a special spine motive series in Germany. Those of course are ordered according the picture they create. The other ones (essentially the US Platinum Series) stand in order of release.