Do-it-yourself brushed controller designs:

www.geocities.com/SouthBeach/Port/1592/electr.htm (click English flag)
www.rcgroups.com/forums/showthread.php?s=&threadid=150584
www.capable.on.ca/rcstuff/escbec.htm
www.math.niu.edu/~behr/RC/speed-ctl.html
www.rcdesign.ru/eng/electronics/esc
www.webx.dk/rc/ecs2b.htm
http://modelhobby.republika.pl/regulator/regler.htm
http://members.tripod.com/~TrEbOr69/speedcnt.html
http://www.welwyn.demon.co.uk/by_me.htm
http://members.tripod.com/Peter_Horvat/myprojects.htm

DIY brushed & brushless controller discussion group:
www.yahoogroups.com/group/osmc