Well, there’s always FF Yoga ;-)
http://www.fontshop.com/search/?q=yoga

Other suggestions:
http://typophile.com/node/67236
http://typophile.com/node/62623

And then there are the red shopping bags from Lululemon with all sorts of inspirational sayings on them...

I do yoga, so any of my types would be appropriate :-)

“A communication regarding yoga” is somewhat vague. If you’re communicating with folks who are already into yoga, any typeface whose chakras are aligned would do. If you're promoting it to the public, you may choose to work with or against stereotype. This is pretty stereotypical...

http://www.myfonts.com/fonts/itc/tempus-sans/

while something as prosaic as Helvetica is not.

I think that is the Yoga typeface from font shop:-)

Great references-especially the alternatives to papyrus. I think Yoga is the typeface Lululemon uses.

Maybe the faces from the Association for Insight Meditation will do...

…if not for the bad karma of plagiarism.

Yoga was created in India, so I suggest a font that looks Indian. It doesn't have to be Indian, but it should have that flavor, somehow.

@Nick – At least it avoids the really bad karma of grotty typefaces.

http://www.myfonts.com/fonts/underware/sauna/