It does seem ridiculous that citizens can be imprisoned for personal use possession of drugs such as marijuana (and, to some degree, cocaine). Certainly, the usage of tobacco and alcohol could be considered at least as dangerous to the human body as the aforementioned illegal drugs (Charlie Sheen amounts notwithstanding). Decriminalization, fines, drug counseling/education/ rehabilitation, and drug testing still seem to be the most logical alternatives for people who find it impossible to use common sense restraint in such matters.
Drug courts seem to be doing quite well in some parts of the US. In drug courts, the judges get special training and they work as a team with prosecutors, defenders, police, and social service types. The offenders are given a program that is worked out by this team. The offenders have to check back in with the court regularly. In other words, it's sort of like a drug rehab program that is monitored by the judge and the team.
There was a story about this in the Feb. 24 issue of "The Economist." It showed, for example, that one county in Georgia has managed to get recidivism rate of only 4.7% among the people who go to drug court instead of to more traditional courts.
So that seems like a good alternative and you might want to look at that article. Here's a link (but I'm not sure if it only works for me because I subscribe...)
One alternative that desperately needs to be considered is suspending custodial sentencing and opting instead for community based reintegration programmes that also give drug addicts the help/counselling/support they need to be able to go cold turkey and overcome their addictions. Putting drug offenders in prison is not an answer to the offender's problem, nor is it going to be beneficial long term to society. There are a variety of residential programmes that can be utilised which have the benefits of taking offenders out of their context but not putting them in an even worse context (prison) and also giving them access to medication, counselling and retraining as necessary. A much smarter option in my opinion.
A change in the drug laws would help. It would cut down the crime assosiated with drug use and allow the users to get on with their lives instead of being arrested for possession/committing crime to fund their habits etc etc. Check out 'Transform' after the war on drugs:policy for legislaion