I don't know where specifically to look but these organizations are doing cool (and positive) things with tech:

Raising political awareness and transparency - http://sunlightfoundation.com/ - https://www.govtrack.us/ - https://www.popvox.com/

Defending rights in the information age - http://www.fightforthefuture.org/ - https://www.eff.org/

Alternative fundraising: helping the little guy raise money - http://www.indiegogo.com/ - https://www.wepay.com/

Facilitating online activism campaigns - https://www.change.org/ - http://front.moveon.org/ - https://secure.avaaz.org/en/