Yohimbe works pretty well, though I wouldn't recommend the dosage by the guy above that took three times the dose. One pill will generally cause increased sexual desire, two should cause much increased sexual desire, and some jitters, though not a lot.
Yohimbe is fun regardless of whether you have erectile problems (I use it recreationally), and is fun when combined with Prozac ... it makes me roll.
Unlike Viagra, which only deals with erections, Yohimbe is actually an aphrodisiac in that it increases sexual desire. It's a fun little drug, it's cheap (a bottle of sixty is $11), and legal.
Purportedly, Yohimbine, the active ingredient, boosts dopamine levels too, which might account for the nice little roll when combined with Prozac. Some trance music helps that, by the way.
Hope this helps. Stop by the drug or sex category on NaughtyLittleVampires.com and let me know what you think.