It sounds like you were the one that got all these parasites into this place, and you're basically just being to damn nice even after you've had enough BS and they are going to take advantage till the bitter end.

Stand up for yourself. Get on your landlord's good side and consider putting ads in the paper and putting the word out with your more respectable freinds that you need some new roomates. Just because you smoke dope doesn't mean you have to tolerate frat boys.

I pretty much totally agree with deadhead65 except that you should stand your ground and make a fresh start right there. Kick all the bums out.

Be in control about it, though. Be methodical. Find actual reasons you want them gone, and if these are young dope smoking guys, the reasons could easily number in the thousands - and write them down. For example, leaving the toilet seat up doesn't really count, that's to easy. But I'd bet there's piss all over the floor near the toilet. That translates into "clean roomate wanted".

Unfortunately, you'll probably wind up with similar roomates in the future unless you make some real efforts to raise your standards in the people you surround yourself with.