You can ( and Aristo did) use power resistors for heaters.
Here are some links to help you out:
http://www.digikey.com/Web%20Export/...f?redirected=1
http://www.caddock.com/whats_new/MP9...ss_release.pdf
http://www.edaboard.com/thread252511.html
http://builders.reprap.org/2009/01/c...ch-heater.html
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