I definitely agree we should promote the site at as many conferences as we can. I have a bunch of OR.SE flyers and SE stickers and would be happy to mail some to anyone who wants to distribute them at conferences. Just send me an email.
I think that's a great idea. There are also local chapters of INFORMS in different cities (a list of US and some international chapters can be found here) that have events. That, plus hopefully help from student chapters, can be another avenue for outreach.