A visit to The Smoking Gun revealed 14 pages describing the large amount of circumstantial evidence against Ivins. The report includes excerpts from emails written by Ivins that paint the picture of a mentally disturbed man. The report also includes evidence that links Ivins to the envelopes, the false return addresses on the "anthrax letters," as well as the intended targets of the letters. His link to senators Tom Daschle and Patrick Leahy was particularly interesting as it appears to stem from their stance on abortion.
Although I would like to read more of the unsealed documents, I am already much more satisfied with this information than the speculative crap described in the media.
You can read the report here.