We're continuing converting all popular and intensive database queries into using our memcached system instead. We're not done, though... we have one last query to convert, and then most of our 20 million+ page views per day won't even hit the databases. Because the databases are generally the limiting factor, involving slow moving parts, removing our dependence on them keeps making the site faster.
We've also orded a bunch of new webservers, even though we don't need them. We just know from experience that web node CPU will be the next bottleneck... it always jumps back and forth between web servers and the backend. Now that the backend is perfectly scalable with memcache, all we have to do is keep buying web servers, which is easy.
Also of note: We have some monster disk storage on its way and we're working on getting a lot more bandwidth. (or rather, getting better bandwidth rates by committing to higher minimums) We'll soon be offering options to upload large pictures for the userinfo page, posting by camera phone, and making mp3 posts from your phone. All these things were infeasible in the past, but with tons of disk and tons of bandwidth, it's play time....
Have a nice weekend!