They've got muck; we've got rakes. TPM Muckraker
On the key question of potential illegal conduct, it finds:
While some of the advice and counsel given by ACORN employees and volunteers was clearly inappropriate and unprofessional, we did not find a pattern of intentional, illegal conduct by ACORN staff; in fact, there is no evidence that action, illegal or otherwise, was taken by any ACORN employee on behalf of the videographers.
Harshbarger also notes that the videos were sometimes less than perfect representations of the events they depict. He writes:
The videos that have been released appear to have been edited, in some cases substantially, including the insertion of a substitute voiceover for significant portions of Mr. O'Keefe's and Ms. Giles's comments, which makes it difficult to determine the questions to which ACORN employees are responding. A comparison of the publicly available transcripts to the released videos confirms that large portions of the original video have been omitted from the released versions.
In the wake of the scandal, Congress voted to cut off all federal funds from ACORN. In response, the group is suing the US government, arguing that the measure is a bill of attainder, and therefore unconstitutional.
Robert Borosage, of the progressive Campaign for America's Future, responded to the report's findings by declaring that "an organization that has done remarkable work organizing and empowering the poorest Americans was targeted and slurred by a right-wing hit team, then persecuted by legislators who should have known better."
You can read the full report here (pdf).