the hope bloc is the semi-sarcastic name given (by outsiders) to a plan for anarchists to attend the obama inauguration ceremony.
because the organizers were worried about anarchists being seen as too critical of the first u.s. black president (and hence being perceived as racist), the plan was for people to dress in bright, happy colors, and to talk to people in the crowd about how the real victory was of people's power (ie all the people who got the first black president elected).
need i say more?