<p><pre><code> 1. Ads of some kind
2. Cross-reference with campaign contribution data from FEC.gov or opensecrets.org
3. I like maps
4. ???
5. PROFIT
</code></pre>
Seriously though, politically active people love this kind of stuff and although the number of people who like to pore over such data is small they also love posting their findings which will result in regular waves - not many sticky users, but you can probably pick up some revenue by CPI ads or beachcombing the serious users with a freemium model.<p>The trick (if it doesn't consume too much in the way of resources) is to join up the disparate information - even though interested researchers could use your site and existing contributions databases to do so now, you'll only get a footnote credit. If there's a nice way to cross-reference the 13f data with other things, then they'll send people directly there, and a percentage of them will surf around and then announce discoveries of their own in a me-too fashion.<p>The reasons I think of political campaign contributions as a cross-reference: political people tend to be obsessed; they're usually quite partisan, so once they've found a resource they like such as yours, they tend to be loyal to it; election cycles, like SEC declarations, take place on a fixed schedule and are thus predictable (in terms of adwords or external marketing); interest is growing in this issue after January's Supreme Court decision to remove limits on corporate campaign spending.<p>Regarding maps, everyone likes them and they're more accessible than tables. but I'm also thinking of more abstract maps, like using processing.js or something to do dynamic node-based diagrams that would make it easy for people to surf the data without consuming much in the way of server resources. I love spreadsheets myself but that's because I'm OK at number crunching - for most people it's the equivalent of trying to make a picture using a mouse and MS Paint vs a tablet and Adobe Illustrator.