Well.. Armstrong had some tests report showing he was taking some illegal drugs, but his lawyers contested that and said it was tampered with and not treated correctly.. and they won in the first instance and now he has spent all his money he got to clear his name in court. I for one are almost 100% certain he wasn't clean.
Rasmussen.. well.. he has missed 4 instances when the testers came to where he said he were and he wasn't there. All his tests have shown no sign of drugs though.. so far.
The guys I feel the most for... are those poor blokes in their teams fighting each stage to keep the "leaders" with the others, biking until their heart almost bursts before loosing 10 mins the last mountain... only to find out the person they've fought for has used drugs and all their work is for nothing.
But then again.. which sport is clean? I just wish they could ban cheaters, in any sport, for life! And if you get caught once in a test you loose any medals you've earned (even if you took them 10-20 years ago), your eventual records will be deleted, you have to pay back all the money you got from sponsors and so forth and you're forbidden to work with any sport in the future.