Espript will produce nice Postscript plots from aligned sequences, highlighting secondary structure: http://espript.ibcp.fr . Roman Laskowski's program PDBSUM seems to fulfill a similar purpose.
Pro-origami: http://munk.csse.unimelb.edu.au/pro-origami/ - and see links on its website!
CCP4's Topdraw is a drawing tool to help you make your own topology drawing.
PDBsum Generate: Upload your PDB file and it will output the 2D topology diagram.