IIR Filter Design (courtesy of dspguru.com links)
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Meteor (Open Source)
http://www.nyx.net/~wliu/filter.html
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DISPRO (Freeware DOS based)
http://www.digitalfilterdesign.com/DISPRO%20Download.htm
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MKFilter (Web Based)
http://www-users.cs.york.ac.uk/~fisher/mkfilter/trad.html