Nichrome wire or a string of power resistors and some method of controlling the current flow is all that is required. There are quite a few DIY web pages out there if you are handy with a soldering iron:
http://www.olle-eriksson.com/Default...Article&id=116
http://www3.sympatico.ca/mark.kaye/dewheat.htm
http://mysite.verizon.net/res0owmd/id1.html
Try Google for more.