[R] density plot for very large dataset

[Obi Griffith]

I'm new to R and am trying to perform a simple, yet problematic task.  I 
have two variables for which I would like to measure the correlation and 
plot versus each other.  However, I have ~30 million data points 
measurements of each variable.  I can read this into R from file and 
produce a plot with plot(x0, x1) but as you would expect, its not pretty 
to look at and produces a postscript file of about 700MB.  A google 
search found a few mentions of doing density plots but they seemed to 
assume you already have the density matrix.  Can anyone point me in the 
right direction, keeping in mind that I am a complete R newbie.

Obi