Actually, there isn't any evidence of Lance Armstrong taking steroids during any of his Tour victories, and nothing similar to what just happened to Landis happened to Armstrong. As far as Armstrong's case is concerned, there were many who were willing to testify he did, but no evidence ever came up, neither during his Tour victories or afterwards.
Here's a summary of how the latest attempt to link him to doping fell through by Dutch investigators:
http://www.breitbart.com/news/2006/05/31/D8HUPHU00.html
As far as Ullrich is concerned, for someone who attests he is innocent, he sure doesn't want anyone to do any further tests on him. And yes, he and the potential winner Ivan Basso (as well as last year's 4th and 5th placed riders - so 2nd through 5th in total) were found to be linked to doping before the Tour.