I popped over to Arduino SE, as I was planning on asking a question or two. However, I got side-tracked by some meta posts, some that we really could do with.
First off, they linked to a SE blog-post that I think we should all read, as I think it should help grow the community.
We've actually hit on several of the topics mentioned there, we've had Is {X} on-topic questions, we have a topic for the creation of the logo, I believe we have a few How do I tag {X} question meta Qs, as well as (I think), who should the moderators be.
The ones we've missed are What should our documentation say, What's the site's elevator pitch?, What should the site design be?, and How should we promote our site?. Please correct (and forgive ;D) me if I'm wrong. Edit: @Jivings has pointed out in his answer that we do have a site pitch question as well as several promotion ones :) My bad, it was late when I wrote this ;P
I will try and create some of those, as I believe they are very important in a Beta's life cycle to graduation.
Beyond the Beta related stuff (not that it isn't important, it is, very much so) there is a very well-done post by @AsheeshR over on the Arduino Meta site regarding voting, especially upvoting, which you can read here. He includes two links that make a lot of sense, and I suggest you read them.
Final thing, Arduino Project Showcase Contest thingy.
Awesome idea, I think it would hopefully bring some more user integration. Arduino's had a fair amount of attention for a site as small as theirs. I know that this was because of Arduino hitting 10 years, which, for the RPi, is quite-a-ways-off, but I think this would be something fun to remember for the future.
We are a very effective site, just look at the stats. Over 13,000 hits a day. People use us, 8.6 questions per day w. a 2.0 answer ratio. 78% answered, not the best, but still okay. We are an active site that is used and referenced a lot.
I think we need to start considering a few more of these things, and then actually following through on them. Read over those links I gave, and let's keep on keeping on :D