It's easy to burn 15 minutes on hotornot.com without even realizing what you're doing, but once it sinks in that you've derived mindless (but considerable) enjoyment from rating pictures of complete strangers on a hotness gradient of 1 through 10, it's enough to make you wish the Internet never existed.
If you still want to keep the Web's comparative hotness possibilities in your life but are looking for something a bit more substantive, try Sexy Science, a blog about—you guessed it—hot scientists. Although it lacks the interactive rating system, Sexy Science gets a bit more analytical, touting the attractiveness of various researchers and grad students from around the country while factoring in things like their ability to "prepare reactive transition metal complexes stabilized by appropriately designed auxiliary ligands." Currently the blog uses a chili-pepper-based rating scale, but it can only be a matter of time before a more precise thermodynamic system is implemented. —John Mahoney