I've bandied about the idea of creating a hard, puzzle race that players can participate and compete each other against on either Friday or Saturday at something like 9pm EST. This is similar to what other gaming communities may do. Anyway, thoughts, players interested, questions, etc.?
A single puzzle version of this was done in eternacon, and I had much fun (hog's creation). Also, I and Astro are on a race for finishing the first 500 3 switch malcolm puzzles (including the future ones), which really helps keeping me from losing interest in the site.
However, Eli once mentioned to me for my dailies idea that a content that makes people be less active in labs shouldn't be put in without consideration (to which I agree and isn't what I think you are doing in any way). Of course, when there are no labs, like right now, it is a great thing to do so people don't lose interest in the game. However we need to think what to do to make it synergize with labs, rather than compete with them.
Also, I think that there should be more than one hour each week when we can participate, as 9pm EST is after midnight for parts of Europe + the middle east. Or maybe make it a "weekend challange", that is open all of the weekend? The problem then becomes that people with a lot of free time get an advantage over those without a lot of free time, and it becomes much more time consuming.
And one final technical note- in the eternacon race, the lab panel in the main page had 2 states, one for the lab and one for the race. It should probably be used in something like this.