Though very helpful for those looking for a new TV or monitor, DisplayLag.com just sounds depressing. I get depressed when I think about how much rhythm games suck on consoles now. I'll never get a new PaRappa the Rapper game.
DisplayLag.com is a database of tested televisions and monitors, with each unit's input lag measured in milliseconds. A display with 19ms or less lag is deemed 'excellent' on their rating scale, while those below 63ms are labeled as 'bad' ones. The list isn't long now, but they say that they'll continually update it as sets are tested, and that you can follow them on Twitter for updates.
The site was founded by Adeel Soomro, also known as "Four Wude," a tournament Street Fighter player. He hopes this effort will establish a new standard for displays in competitive gaming.
Not to brag (mostly because it's inexpensive), but the best rated display on the list when sorted by input lag is my current PC game rig monitor, the 23" ASUS VH236H.
On the other hand, my big-ass 70" Sharp 3D HDTV isn't on the list, but from the looks of others on the list, it sucks as far as input lag is concerned. I've got a 55" Sony LCD that fares better, though.