Right now, you have a choice of learning
PSTricks or
PGF/Tikz for all your drawing needs. Both are large pieces of work which require you to read the manual over and over again. At least till you get it.
For myself, while I've known about
PSTricks, I've stuck to
PGF/Tikz. But if you need to have better plotting and more features than the already extensive one in
PGF/Tikz, then
PSTricks is the way to go. Again, the choice is dependant on your needs and the level of programming you'd like to get into.
This
thread on
comp.text.tex might help you decide.
EDIT: As the note in the comments mentioned there is also
METAPOST and one other graphical language called
Asymptote.
