I have a 6 x 10 trailer. It's pretty packed also.
This is what I currently keep in it:
(1) screen (size depending on current event)
(4) speaker stands
(2) EON 15 G2
(2) EON 10 G2
(1) JRX118SP Subwoffer
(1) 10' truss w/stands and "T" bars
(4) DJ lights
(1) DJ case w/projector, DVD player, mixer, etc.
(2) 6' folding tables
(2) tripod mounted dual spot lights
(1) popcorn machine w/cart
(6) cases of popcorn
(2) cases of popcorn boxes
(2) cases of glow sticks
(3) folding chairs (for myself and my help to sit on during movie)
Various brooms, dustpans
And about 950 million extension cords/cables (you never know what you'll need)
If it's a music video event, I load my DJ computer.
If it's a video game event, I load the XBox 360 or Wii, plus games, controllers, etc.
And I probably missed some stuff, but that's the basic stuff.
I took some pics of my trailer and current setup. I have been meaning to start a "Trailer" thread, this seems like a good time. I'll edit this post with a link as soon as I put it up.
I just posted a thread with pics of my trailer/setup: