Hi all,
We have 12,500 registered users on our site and are still trying to figure out how to make $$$ with the site. Any ideas?
Thanks in advance!

Okay - two things I can do for you.
For free, I can suggest that you look into advertising providers or start a sponsorship/advertising program of your own.

For a service, I can provide details of several Advertising companies that could supply you with CPM advertising (pays by the thousand for page impressions/hits), which is more reliable than PPC (pay per click).
If you are UK based, I may even beable to recommend up to 3 reliable marketing companies for you.

Ah, sod it - I hate being tight and wanting cash

Most advertising companies or online marketing companies havereally shoddy search-engine data, so finding them is a nightmare (go figure).

Look for companies such as Aurora, Doubleclick or Adtech.

I myself would look into my own Sponsorship and Advertising system - as that means you can control what adverts, where they go and how much you get etc.
Depending on what you site is built with/how good you are, you can handle such a thing yourself, (I use Xaraya and use the Articles module ).
Alternative, you can use something like adnews or what not to control your own campaigns, and that has instructions on how to include the advert display code.

Browse through several sites, learn from them, basically just try to think what do they do earn money.

Most popular way is ofcourse advertisements, sponsorship and providing two kind of membership(on paid and other free).