PGF : A Latex macro package for creating graphics. Its usage is
similar to the standard picture environment. I prefer this over drawing
pictures in xfig and then including
it in latex, since with pgf, text written in the drawing inherits the
same font as the rest of the latex file. Also, I get all the power of
Latex's facilities for rendering mathematical formulas inside the pictures
too. Again, a bit time consuming at the beginning, but very powerful and
neat. Dia is a drawing tool
similar to xfig, and can export pictures to pgf.
Here is a small module
I wrote for pgf. When asked to draw a line between two nodes, pgf usually
draws a line between the centers of the two nodes, ending the line at the nodes'
borders. There is no built in facility to draw a line parallel to this default
line. This module adds commands to do this for circle and rectangle nodes. pgfmoduleabshapes.code.tex
contains the command definitions and Example.tex demonstrates the usage,
with some inline documentation in the form of comments. Disclaimer: I don't know
if this module meets pgf's excellent standard of numerical stability. Also,
the pgf manual mentions that this feature is not incorporated for specific technical reasons.
This module may not work properly in some situations, especially when co-ordinate
transformations have been applied. Use at your own risk.