I generally believe the mantra "less is more" is correct. There is a beauty and efficiency in boiiing things down to the most essential. And it is also a design goal we have with our products- even products as incredibly rich as Hoop.la.
When it comes to the content and management of your site though, less is definitely not more.
1. If you use forums, unless there are true privacy concerns, you should make each forum as open as possible. Don't require registration to access your forums. Discussion forums inspire others to participate and post. Locking them down prevents your content from getting out there and stands as a giant barrier to entry for your audience.
2. If you have premium content, make sure you have plenty of it. And Hoop.la already does a great job of teasing that content for you, so your community will see it. People gladly pay to support a site's content, but only if they feel there is value there. (And if you are not offering premium memberships of some kind, you are leaving money on the table.)
3. Include some kind of media with each blog post. Embed at least one photo in each blog post for instance. Adding a visual dimension to your content definitely makes it more appealing. The richer the content, the more appealing.
4. Make your site as multi-dimensional as possible. If your site is primarily a blog, add other components like forums or a calendar to give your site more depth and make your audience feel like more of a community. Hold regular chat events so that everyone can get together at the same time. Schedule offline meetups, if appropriate and your audience/community is large enough.
5. Run ads, even if you won't make much money at first. Some people don't include ads on their site because it's too "commercial". Or because their sites are too small. Or because they don't know how. I'm not advocating annoying your audience by overpopulating your site with ads, but if you are strategic with the placement, they can help you generate some income over time. And the time you put in on your site has value and you should be compensated. Don't feel guilty about it. Even if you are a non profit, I think ads make sense.
6. Promote your content. Twitter is your friend. Each time you post anything new, make sure you tweet it out and promote it in every other way that makes sense for your site. Similarly, make sure your site supports RSS and email notifications for new content so that the people who are familiar with your site can stay in the loop on their term.
7. Don't try to do it all yourself. Add co-writers for your blog. Promote active community members as community moderators. You need as many evangelists and engaged believers in your site as possible.
8. Allow (and be grateful for) comments. Yes, trolls and spammers exist and will be more problematic as your site grows, but to shut down commenting means you have let them win. Use content moderation tools to help you identify the troublemakers and of course make sure your content system support user reporting of improper content.
9. Give your audience as many ways to have a voice as possible! You are in control of your site, but think of yourself as a shepherd and not a dictator. Your goal is to grow your flock and keep them coming back to your pen. And actually, your even bigger goal is to truly understand that you are merely part of that flock yourself.