I just noticed your site and I'm happy you guys made it into beta; I wish you all the best in making this a great site.
One nice way to let the world know about this site is via the Community Ads which are available on fully-grown Stack Exchange sites. There are a bunch of related SE sites and these ads are a potential resource for you guys to find users; for an example see this year's thread in Physics. I've gone ahead and created this image for the Physics site,
but if you guys can come up with something more compelling I'm pretty sure we'll be happy to host it over there. You can then post these in other SE sites and essentially ask their communities to advertise you. If you come up with good material, it can also become a good starting point for your site's graphical identity.
Just something to think about.
So the Community Ads threads have been changed slightly this year to accommodate a change in the width of the sidebar. To match this, here is a new image to the new specifications:
with its corresponding Inkscape SVG source. This runs at double the standard size to provide better resolution for retina display users, whatever that actually is. This one is currently in proposed status on the 2016 Physics thread.