ok first off, i will explain something to you guys...cause i see a couple of you don't know how the memory managment works...
your machine is not sucking up and using all your memory...
run this command in the terminal (and i will show the output of mine for example purposes):
free -m
now as you see i have a total of 628 megs of ram...and it says there is 471 used and 197 free....now i think this is where you guys are getting messed up...my machine is not actually using all that memory for apps and services or whatever it may be...
but if you look to the second line, you will see that most of my memory is cached, and that i am actually only using up 146 megs of my memory, and that there is 481 out of my 628 free...
so to give you a technical explanation of all this read on ....
Both disk buffers and page cache resources will grow until there is very little free memory left. This allows Linux to dynamically create VERY large amounts of these two resources.
When you run a program in Linux, it will check to see if there is free memory available that can be used to store the program. If so, it will allocate that free memory and load the program. If there is not enough free memory, it will examine the disk buffer and page cache resources and shrink them in order to
make free memory that can be used to store your program in memory and run it.
i hope you guys understand the point i am trying to get across...

Yes I understand, DrOzz. But, when your trying to run a program and your cpu is crunching, your RAM is topping out, your HD light is on, that means you need more system resources. You can either add more hardware or lower your usage by turning off services and using lower memory programs such as the window manager.