That's my suggestion, that you can search the games list on an opening or list of moves or a position. I'm pretty sure it will take a lot of code to be done, so it's my Christmas gift to the programmers (the suggestion is the gift, of course).
1. Make code that can classify and index the games by ECO code and/or name of the openning (the ECO code for most of the opennings can be found in the Internet, but for testing purposes I think you can start with the ones at http://chess.about.com/library/ble50ndx.htm?PM=ss13_chess).
2. Add a search box at the Search Public Games that accepts the ECO code, or a drop-down list with the most common ones.
Now the very hard part (it will add some chess database advanced features to the site -- I'm not sure if is it what you programmers want with this chess site, but I think it will attract more chess 'freaks' - you know, the people that will do a search on the people they challenge or are challenged by to see where they suffer more losses on the board):
3. Add a position search feature. You enter the position in FEN or editing a board, and click on Search. First you must add a position list for *all* games (a new move, a new position, look if it is allready at the database, if it's not, add a new entry in the database, else add a link of the game to that position, or something like it)...
With this feature you can answer questions like How good is my oponent (or the player X) at the King's Gambit - 1.e4 e5 2. f4 - openings? and How popular is the Sicilian Defense - 1. e4 c5 - between 1400 or less rated players in this chess site?
I hope you can go out of your coding cave before 2004 Christmas...