Filter synthesis package
http://members.aol.com/faisyn/faisyn.htm
includes the following programs:
http://galeb.etf.bg.ac.yu/~lutovac/afdhome.htm
http://www.ee.surrey.ac.uk/Workshop/advice/coils/index.html
Freeware.
http://www.sherlab.com/electronics/filter.html
Filter design software for electronics engineers and technicians. Filter Wiz for active filter design; OpFil for both passive and active filter design.
http://www.schematica.com
inductor design using powder iron cores
http://www.powerdesigners.com/ChokeDesigner.shtml
Filter design software, microwave, RF, active OP-Amp filters.
http://www.geocities.com/gregsdownloadpage
http://www.eece.ksu.edu/vlsi/spiralmod/