Chemtool
Easystroke
Chemtool relies on transfig by Brian Smith for postscript printing and exporting files in PicTeX and EPS formats. Its companion program, XFig, is recommended for enhancing the output of chemtool, and for creation of 2D diagrams and schematics in general. Both are included with most distributions of Linux, and are available through a number of websites including www.xfig.org. If you want to import chemtool drawings into word processing programs other than LaTeX, you will probably want to add a preview bitmap to them, as neither StarOffice/OpenOffice nor that software from Redmond seem to be able to display postscript inserts on screen without them. For this purpose, using either ps2epsi, which comes with ghostscript, or epstool, a part of gsview is recommended. Since chemtool-1.6, this option is supported directly (through the equivalent function offered by recent versions of transfig).
Chemtool was originally written by Thomas Volk, then a student of chemistry and biology at the university of Ulm, Germany. His version, which was described in an artikel in the german periodical LinuxMagazin, was using plain X11.
I became involved in development shortly after reading this article, adding a few bond types and such, and gradually took over from him as he was lacking time due to his exams drawing near, and probably generally moving on to other things. Note that i am not doing this alone – much of the progress is due to contributions of code, translations, examples or just ideas.