Is there a website that tells you how active multiplayer games are as of now?

The way I do Xbox Live is usually in 1 or 2 month chunks (either I redeem a free month from Bing Rewards, or I get something like a 2 months for $2 deal). When I do, I like to get in all my multiplayer gaming for that month or so, and it's usually all I really want for the year. When I do, I kind of want to maximize all the achievements and stuff I can do. For example, I just got the Bioshock Rapture Bundle, and I'd dip into the Bioshock 2 multiplayer, but if no ones there, I'd just want to know if it's because the time of day or day of the week or whatever.