http://en.wikipedia.org/wiki/List_of_doping_cases_in_cycling
Wikipedia has a great page that outlines the history of doping cases in cycling. I suggest everyone who cares about the future of the sport read it over.
In short, there are about a half-dozen former team members of Postal / Disco who tested positive shortly after leaving the team. They include Heras, Beltran, Landis, and Hamilton.
There are many rivals for the Postal / Disco squads that have tested positive or been sanctioned due to involvement in Operation Puerto. They include Ullrich, Basso, Pantani, Beloki, and Mayo.
Others who have confessed to doping but "got away with it" include former Postal / Disco riders Andreau and S****.
The Wikipedia link makes for some great reading. One thing that stands out for me is that Theunisse tested positive in the 80's and was given a ten-minute time penalty in the TdF, but he was allowed to continue. This sport has seen a lot of changes since then.
Another telling episode was the "Festina Affair". The team car was exposed to have a pharmacy inside of it. Festina was kicked out of the TdF, wholesale. The riders from the other teams staged a protest to the punishment of the Festina squad. Telling bahavior of acceptance of the use of pharmaceuticals in cycling.
One of the interesting portions of the Wikipedia page is that a race "rule book" from the TdF to the riders stated that "drugs would not be provided by the organizers". In other words, you have to bring your own, guys.
Previously, I though Operation Puerto would be the bomb needed to clean up cycling. I now think that the federal investigation against Postal might be that bomb. When the consequences of doping change form a ten-minute penalty to a two-year ban and then to a risk of incarceration for a federal crime of fraud/perjury, change is immenent.
I hope the best for cycling and fair sport in general.