the poster in post 10 linked and listed the steps. It seems to me that a movement would be needed to be organized in each state. Some of the Senators are up for reelection so it'd be more effective effort wise to work against their reelection but in the cases where the senator is not up for reelection in 2010 it would be up to someone within each state to organize a recall campaign.
There has never been a successful recall but what could rise above violating the constitution and one's oath of office as grounds for a recall?