A friend asked me for a couple thoughts on how to "open up" their website. Happy to oblige. BTW, Dion Hinchcliffe offered some thoughts a while ago that may be more helpful than what i've provided.

So, here's the setup: Imagine you have a top-ten website (in your category), one where there's a big database of content and images that you know people value. In this example, imagine it's a database of cycling related news stories and bike vendors. Think of Bikeradar.com or something simiilar. Your site has a large and growing database of "members" who can comment on stories, rate vendors, and get emails from you regularly.

Step 1: Accept content from members
This is pretty obvious, but make it super easy for consumers to contribute stories, images, ratings, reviews etc. I know you're already planning this.

Step 2: Turn over Editorial to Consumers
Don't just outsource the content creation to consumers, but give them the reigns for editing and organizing the content. Give them the tools to create their own unique versions of the content that would be available to other visitors to the site. On food sites, they're called recipe books, collections, etc. Here, they might be notebooks, "top ten" lists, etc.

Step 3: Reward and Incent this Behavior
Not necessarily with money, but some sort of recognition or acknowledgement of the effort. Whether its a reputation system or something done by the site editorial team, you should try to encourage and stimulate this activity. It's a pretty straightforward strategy that leverages the network effect: You want a system that gets better when:

• people get more involved
• more people participate

Think of Flickr: It's better when more people are creating, managing and editing groups of photos AND photographers, The higher level of participation creates more value for heavy users (rewards/recognition) and more value for casual users: organization, discoverability, findability

Step 4: Make it Easy for Individuals To Share Your (Their) Stuff…Casually
If i'm a blogger, and i'm affiliated with Bikeradar.com, i should be able to show/use/share/distribute the "stuff" ive created on Bikeradar.com with everyone else that comes to my blog. So, i should be able to share my bikeradar.com stuff – collections of artciles, the tips i contributed, the collections ive made, the reputation i've gained  – on my blog. It's valuable on Bikeradar.com, but it's also valuable to the visitors to my blog. Becase a) i made it b) I've added value (organization, comments, etc.) to already valuable content and c) My association with it gives it added relevance to the audience who comes to my blog. Look at Flicr badges, facebook widgets, etc.

Step 5: Make it Easy for Organizations to Use your Stuff…Systematically
You're goal is to get your stuff (your brand, your content, your services) out there and distributed. And, while you're super smart, you can't do everything and certainly can't think of all the ways people could use your bikeradar.com content. So, Make it easy for trusted, validated partners to access your database(s) and use that data. An open, documented, easy API is a must. Your goal: enable a service from your content.

Look at some of the early work around BestBuy's "connect" program. Or, the number of organizations that are using the amazon API. And, of course, look at what Flickr and 37Signals (Basecamp) have done with their API's. Both Flickr and 37Signals have enabled the development of ecosystems around their base tools. There are now hundreds (Flickr) and many tens (Basecamp) of applications – both free and paid – that  have grown up around those companies. And these eco-applications have made the base app that much more valuable.