While all the answers you have been given thus far are absolutely correct, what they are failing to understand is what is the underling question: How to I, as a 'total geek with a need to control all aspects of my techno-life" (<- tongue and cheek), gain total control over MY machine?!
I get this... I hate when apps and processes are run on my machine and I don't understand what they are doing.
Let me first point you too a really great site that will give you a clear list of each process that is running :http://triviaware.com/macprocess/all. This site will let you upload a text file (that you collect threw your terminal app by running:
"ps -A > process.txt". You will then upload it and get the definitions of each thing you are running.
Once you have that info you will be able to determine what you might be able to kill off and if you really want to.
Next spend a little time in your ~/Library folder and look into "LaunchDaemons" & "LaunchAgents". This is where all the process that start up with your account live. You should also look into your "StartupItems" while your there.
Now if your really want to go crazy look into your /System/Library folder and look at the same folders in there. This is where all the process are that Apple wants you to run. You can go nutz!
All that said I give you this fair warning!!!! Mess around in these folders all you want but know you can TOTALY SCREW UP your machine to the point of needing to do a total rebuild. So before you start make a complete and total backup of everything!!!
So from one control freak to another... Good luck in your chase to become a master of your environment! It's taken me 28 years and I'm only 3/4 of the way there. :-)