"Was it a dream where you see yourself standing in sort of sun-god robes on a pyramid, with a thousand naked women screaming and throwing little pickles at you?"
from one of my favorite movies of all time...
seriously though, when i was in college (and had a lot more time on my hands) i read a few books on 'lucid dreaming'. The Queensryche song Silent Lucidity touches on this subject a little bit, and volumes have been written about it.
It's the ability to control your dreams...you can really do some amazing stuff without all that physical-world stuff bogging you down.
The two real important things you can do are
1. keep a dream journal...write down everything you remember as soon as you wake up - as much detail as possible. Keep it nearby during the day if you can, because sometimes a day's event will trigger a memory of a dream.
2. ask your self periodically, throughout the day 'am i dreaming?' and answer yourself ("no", of course). If you do this while awake, presumably you'll ask yourself during a dream and realize that you might answer 'yes' to that question.
Once you're able to cross that barrier, the wall between your conscious and unconscious mind starts to break down and you can control what's happening. Some consider it an out of body experience.
None of this is very easy...I actually "got there" one time that i can remember. It kinda felt like i was rising up out of my body, still lying in my bed. I flew out my bedroom window and down the block before my conscious mind said 'ummmm...no'.
If you've never flown in your dreams before it's pretty awesome. It's a good 'first goal' to set if you try to undergo lucid dreaming.
Oh...one tip...you're most likely to become lucid shortly before waking up. What i used to do (and it worked) was to set my alarm for an hour or so before i actually had to wake up...get up for a few minutes, reset the alarm for the correct wake up time, and go back to sleep 'til the alarm went off. It's that 'half in/half out' kinda feeling you want.
Give it a shot! Don't let your brain dictate what you dream about!
I took a nap on my couch this morning while listening to the "an evening with Kevin Smith" DVD...had a dream I'd fallen asleep on my neighbor's couch while watching it. It was real as could be. I felt weird seeing them later in the day, because they were in the dream wondering why i was sleeping on their couch.