My experiences with sex on the following drugs:
SHROOMS - Don't ask me why I thought it'd be worth trying to have sex on shrooms. Your brain goes in a thousand directions and every minute feels like a new day. My partner tried touching me first and I got giggly and felt like I couldn't focus, so I said I would touch him instead. So I slipped under the covers, took out his penis...and suddenly realized I was in a MAGICAL CAVE WITH A DRAGON (his penis). I started playing very non-sexually down there and having a great time by myself, while he laid there uncomfortably in silence and finally told me to stop. That was the end of that attempt.
ECSTASY - I had high hopes for this, but in the end it was anticlimactic. Apparently guys have difficulty sustaining erections under the influence, which was certainly true for us. And while it felt great to have him inside me, the truth is, EVERYTHING feels great on ecstasy. Sex on ecstasy felt as good as touching someone's face on ecstasy. But I guess everyone is different. Ecstasy is my favorite drug, I just don't care to have sex on it.
In the end, I think plain old drunk sex is my favorite "under the influence" sex. Alcohol makes me horny!