Jesusgreen
Bluelight Crew
I quite like this chart: http://en.wikipedia.org/wiki/User:TheJamerson#Psychoactive_drug_chart
Cannabis has such a large variety of effects, which is why it's hard to classify it. It's the depressant effects that make it synergise well with benzos/alcohol/opiates/etc - you'll notice though when combining it with depressants that the strange thought trains and such are likely to cease or lesson. The same is true when combining benzos with psychedelics - you generally need quite a high dose to completely kill a trip, but they usually lessen the mindfuck before anything else.
Cannabis has such a large variety of effects, which is why it's hard to classify it. It's the depressant effects that make it synergise well with benzos/alcohol/opiates/etc - you'll notice though when combining it with depressants that the strange thought trains and such are likely to cease or lesson. The same is true when combining benzos with psychedelics - you generally need quite a high dose to completely kill a trip, but they usually lessen the mindfuck before anything else.