It's making its appearance on new MacBook Pro models and it's promising 10Gb/second transfer rates. That's dual-channel, too so you'll get 10Gb/sec both to and from your devices. Apple suggests this will be useful for external RAID arrays, Gigabit Ethernet adapters, and also mentions support for "FireWire and USB consumer devices" along with HDMI, DVI, and VGA over DisplayPort. Apple expects that Thunderbolt will be "widely adopted as a new standard for high performance I/O," but we think the USB 3.0 crew might have a thing or two to say about that. Full PR is embedded below.
Update: Intel has thrown up its page on the technology, and it looks like the Light Peak name is officially no more. Intel indicates this speed will be enough to transfer a full-length HD movie in less than 30 seconds -- but doesn't indicate the bitrate of said film. Intel also reinforces that this is compatible with existing DisplayPort devices and it also uses the PCI Express protocol for enhanced compatibility. Daisy-chaining will be possible, along with bus-powered devices, and cables can be made using either optical or electrical construction.