Depends on how you mean 'techno'.
If you mean it in the purest sense:
http://www.shoutcast.com/directory/?sgenre=Techno
If not then use the genre selection on the right to choose other genres under 'Electronic'.
http://www.bbc.co.uk/1xtra/ hosts 2 of my favorite dnb radio shows (dj flight and dj bailey). They're free of the fluff that rider and fabio have. Of course there are a ton of dnb stations on shoutcast.com as well, use the genre menu to find them.
http://www.thewomb.com/ was one of the stations to fight the CARP ruling (online copyright fees for broadcasts in the US). Go into
http://www.wombmusic.com/ and check the upper left hand menu.
Personally I just check out shoutcast's ambient & downtempo lists. The Dnb stations are ok depending on what live dj is on (me!) but i'm not a big fan of dancefloor tunes track by track (unmixed). Same goes for a lot of other shoutcast stations, so get to know your dj timeslots if there's something specific you're after.