I've hit a brick wall; what could I possibly add next?

[MPDev]

It's that time of year when I start to look for the next 'big thing' to add to the website; it started with PhotoPost Galleries which after all this time have become a "must have" for any forum I run and get used as frequently as the forums, then on my fitness site it was adding a Fitness Blog and Workout Tracker - those are picking up nicely. My homebrewed radio station does well (Pink Floyd all day long, even hired a professional to do station ids) as does a custom Owners section which lets users upload info about their cars, link to products in the Reviews section which links to vendors and their products, etc.

I have personalized websites for our users which gives them a web-based front-end for creating flash based websites, and integrated webmail and even POP accounts for supporters.

Integrated chat, yawn. Classifieds, nice and useful, but not very exciting.

I've tried things like vBookie and other mods to try and get people into some kind of activity that is fun for a larger group, but that was great for about a week and then interest trailed off.

Some kind of networking Texas Hold 'Em would probably be great; but that seems like a serious undertaking and there are plenty of Windows/Mac versions of networked games that can be played.

So, I'm left thinking - what's next? What's something new and exciting that users will flock to and find entertaining and useful?