Leonard Nimoy on NPR last year said he was at a Chicago Democratic fundraiser before Obama ran for President and Obama noticed Nimoy and gave the Vulcan salute to him.
Oh and one point Newsweek said that Obama thought his wife's belt looked like a star trek communicator and shouted into her belt something about dilithium crystals.
The fact he knows what a Dlithium Crystal is is pretty good 'Trek cred I'd say.
I think that happened on the night of his Primary win. Michelle was wearing her favorite belt which kinda looks "spacey", and Obama spotted it before they went out to greet the crowd. he bent down, poked at the belt, and said, "Ooh, dilithium crystals! Beam me up, Scotty!"
I am paraphrasing. it's in one of the articles I read about that night. I'll try to find the link sometime.
yeah, he's a Trekkie. not obsessed, but, I suspect, a slightly more than casual one.