From what I understand there is only one study on the relationship between creativity and LSD:

Psychedelic agents in creative problem-solving: a pilot study. Harman WW, McKim RH, Mogar RE, Fadiman J, Stolaroff MJ. Psychol Rep. 1966 Aug;19(1):211-27.

http://en.wikipedia.org/wiki/Psychedelics_in_problem-solving...

The results suggested that LSD has a positive effect on creative problem solving. I think it is a shame that no follow-up experiments have been conducted.