If you want both monitors to display the same thing, a splitter will do.
If you want them to be different, you'll need to either...
A) Pickup a cheapy/used PCI video card.
B)Use the *-Video out to a TV
I don't believe there is an *-Video -> VGA adapter out there... but I could be wrong.
Once you've done either of the above, go into Display, and "Enable" monitor #2.
I run 3 monitors on my machine, with 3 different video cards... it'* like widescreen.. I love it. AIW Radeon 8500DV AGP & 32mb TNT2 PCI (x2)
*SOLD* - Turbocharged - 1991 Bonneville SSE
*SOLD* - Supercharged - 1997 Bonneville SSEi