I want a drug that's like marijuana but is 1) substantially less potent and 2) doesn't impair memory. The reason for this is that I've noticed that while under the influence of small amounts of marijuana, the "connection-making" circuit in my brain is far more active. Of course, if it's too active then this is an impairment (everything becomes "connected"). But I'd rather have to reject spurious connections than to not have access to potentially insightful connections in the first place.

You will get this effect from taking Aniracetam (or the other 'racetams). A lot of the other things I can think of in this category are more intrusive than pot is.

A smaller amount of marijuana?

Jonathan Lehrer in the excerpts from his new creativity book mentions that alcohol has been shown to help 'insight' problems.