I've found several tools that work for my drawings, depending on the
application.
Inkscape is my favorite for diagrams or sketches of graphs. I can point
you to one diagram I just made with it for my Chemistry class:
http://www.flickr.com/photos/waski_the_squirrel/4079787050/
You can also find my original diagram from before LaTeX and Inkscape in
the same location.
For plots of data, I like Rlplot (which comes with my Ubuntu
distribution). It exports data and mathematical functions as .svg files
and they appear to be quite precise.
I've occasionally used the graphics of LaTeX for diagrams: TikZ and
pstricks. I have only limited skill with these and, while I'm impressed
with the results, I don't see the investment of time to be worth the
return I get. Maybe in the future...
Anyway, match the tool with the need, and spend some time considering
what exactly you want to do.
I jumped into this discussion late, but I hope this helps.
--Jason Waskiewicz
Bowman County High School
