1. There is an excellent noncommercial program called MacMolecule, available
at ftp sites like IuBio(I think). It draws space-filling models of large
and small molecules. It is pretty slow in rotation, but the graphics are
outstanding.
2. There is a commercial program called MacImdat (about $2000) which also
displays molecules. It has a horrible (for a mac) unix-style interface, but
works rapidly with much larger molecules than MacMolecule. Some labs at
UCLA have used it on whole immunoglobin molecules. Graphics can be exported
to programs like PixelPaint.
-Peter Markiewicz