While Xinerama is the most popular of the dual-head options, there are others:
cloned (same thing on both screens -- not very interesting),
dual X sessions (each screen is independent and does not communicate with the other),
Xinerama (one big screen, but slow because there is no hardware acceleration), and
Merged Frame Buffer (like Xinerama, but with hardware acceleration).
All of these are handled through xorg.conf (or XF86Config) and while it is not hard, it is a tad arcane. But Solarin is right, once you get it working you need not do it again.
FWIW, I usually use Xinerama with an old Matrox G450 with dual 19" tubes. It works very well indeed.