What about writing tutorials/articles? There's www.openbsdsupport.org which I believe is officially blessed though it doesn't look too active. Probably for lack of people submitting articles :-)
Of course if you have a blog or web site you can write OpenBSD stuff for it. I know I've sometimes struggled with putting the pieces together where a step-by-step "how to accomplish X" with OpenBSD would have helped. Just last week, Ted Unangst's "what I wish I known before setting up OpenBSD on my Beagle Bone Black" on his blog saved me a lot of time and frustration.
