Chemtool is a GTK+-based 2D chemical structure editor for X11. Drawings can be exported in XFig format for further annotation, or as Postscript files (using xfig's companion program transfig). A set of sample molecular structure drawings is included in the archive.
KMol calculates molecular weights and elemental compositon of compounds from their chemical formula. KMol supports user defined groups, unlimited number of nested subgroups, multicomponent compounds, global and per-user symbol definitions.