I used to put in a lot of Smashing Pumpkins

Mellon Collie and the Infinite Sadness is a great album to just have on. Not one of my favorites but when I was high I could listen to it over and over.

Pisces Iscariot was also another great one.

siva and Siamese Dream were both great albums to just kick back to as well.

I think the thing about Smashing Pumpkins music is that it is not really aggressive but it's not overly mellow either and it has a lot of layers to get lost in.