I don't see any link on the main Mathematica.SE page that leads directly to http://meta.mathematica.stackexchange.com. There is a panel in the top-right corner that links to "Hot Meta Posts", but this requires an additional click from one of those posts to the main meta page. I think there should be a clearer, straightforward and more visible way to access the meta page so more users are aware of its existance and purpose. I can speak from my own experience, it took me quite a while to notice it and start using it.
In the upper left corner, next to the recent achievements and the inbox there is a link list to all StackExchange sites.
@Karsten 7.'s answer made me look harder at the main site's menu bar and I actually found the second way to access the meta site - through the
Conveniently, you can also return back to the main site using the same menu while browsing the meta pages.