Gateway Pundit [now defunct blog] has an excellent survey of ACORN-sponsored voter fraud:

The Complete Guide to ACORN Voter Fraud-- 14 States Investigate Obama's Community Organization

And, you thought 2000 was bad? This year's election is shaping up to be one of the most controversial in history. Just this week a federal judge ordered Ohio's top elections official to verify the identity of newly registered voters by matching them with other government documents. The very next day a 6th U.S. Circuit Court of Appeals set aside the federal judge's order on verifying registrations. And, so it goes.

To further ignite the voter fraud-voter registration debate this week was the news that a national community organizing group is being investigated in at least 14 states and several swing states for massive voter registration irregularities. This news would make headlines anyway but what made it worse was that Barack Obama worked for this organization, the Association of Community Organizations for Reform Now, in the past. Obama trained its local leaders, represented the organization in court, and worked to funnel funds to the organization. The Obama Campaign also donated $800,000 this year to an ACORN affiliate.

I thought to myself why should I not profit from the current Obamamania and so I designed the following tee-shirt: