Looking good naked is the best aphrodisiac.
Going out into the woods, killing things, bringing them home, and waving the bloody dead bodies at my wife has worked well for me, but looking better naked ain't bad either.
I think eating healthy and taking care of yourself is the best aid there is. It makes you have more energy and feel better about yourself. Nothing sexier in my book.
"Oysters are high in zinc, which raises sperm and testosterone production. Oysters also contain dopamine, a hormone known to increase libido."
Maca root (powder or extract) seems to be somewhat effective: http://www.ncbi.nlm.nih.gov/pubmed/18801111
Good for sperm count? http://www.ncbi.nlm.nih.gov/pubmed/11753476
Pubmed has a ton of stuff about it.