I don't disagree with what you are saying. Here are my thoughts.
I think Andrew is doing some pretty good things already here. Getting OSR publishers to call OSRGaming.org their forum home is a great step. Mischief, Inc. is doing some web redesign, and OSRGaming.org will be linked through our forum links on our Main web site, our blog, our storefront and possibly a wiki. It would be great to see the other publishers here making the same changes/commitment.
I think leveraging social media is a great idea. If OSRGaming.org does not already have a Facebook and Google+ page, and Twitter account Andrew should add those as soon as he can. Posts and tweets to those accounts would link back to interesting posts here on the forums. At the very least, as soon as you make those posts/tweets, there will be dozens of spider bots crawling all over these forums which should add to search engine visibility. Make sure you hashtag #DnD and the DnD Twitter account will almost certainly re-tweet your tweet.
Good old fashioned footwork cannot be replaced anything else though. Members here should get the word out and try to get members of their gaming groups to join up here. If you game at a brick and mortar store with open tables, talk to the other groups playing. If they have an interest in old school play style, write down the address for them.
Also I think there needs to be a file repository for free content. I think that's what the Downloads link above is supposed to be for, but I'll be damned if I can figure out how to upload anything. Mischief, Inc. has a free product we would upload, and two more on the way this year.
Finally wrapping back to the publisher angle. Engage the publishers on OSRGaming.org. Don't let us just hang back and make advertisement posts when we have a Kickstarter coming up, or when we have a sale. Become patrons of our products and when you have questions about something you see in those products, ask questions. Even if you are an old grizzled Dungeon Master who is just going to make something up to fill a gap, or parse some awkward wording on your own, ask anyway. You might be helping someone else down the road who will read those posts and think, "I'm glad I came to OSRGaming.org."
Oh and talk up the atmosphere here. There are other, bigger forums with lots of game design celebrities in residence. Most of them are full of nasty, rude people. OSRGaming.org is different. We're nice and polite. Let EVERYONE know that!