The Counter-Inaugural 2005 website appears to be the main digital hub responsible for the organization of a wide variety of political action groups that, however disparate, do share one common goal: expressing their strong objection to the upcoming presidential inauguration.
Of a numerous list, one of my favorites would have to be a political action group going by the name of Bang!Zoom! Their inaugural day protest takes the form of a collective mooning of the president.

For a full index of all the groups set to converge on Washington, D.C. come inauguration day, click here.