Call me obnoxious, but I pass out cards left and right. I usually give to moms struggling with a baby and trying to get something done, or to moms with babies and toddlers/preschoolers. I try not to come off condescending. I say something like, "I know how hard it is with babies (babies and toddlers--I have two blahblahblah...), having a carrier really helped me so much. Check out X-site (usually the informational, not retail) and NINO. It's purely an informational website." That way they don't think I'm pushing to get a commission or something (not that it's bad, just not my style). And I really do want to spread the word since no one told me about it!
I've never come across many moms using anything else besides a Bjorn, but I'd totally tell them about NINO if I did.
Kristin