Hopefully we'll start seeing them later this year when Intel releases the specification to manufacturers of Windows PCs. Thunderbolt will be included in some chipsets for the Ivy Bridge processor.
In the meantime, the only mainstream Thunderbolt products are the Apple Thunderbolt display, the LaCie drive (which starts at $400), the Sonnet Echo ExpressCard 34 adapter, and several RAID hard drive products geared toward the enterprise.
I have used the Sonnet Echo ExpressCard 34 adapter to add an eSATA adapter that I use for a backup drive, but it is fairly pricey. Besides the $50 for the cable, the adapter is $149, and the eSATA card was another $15.