With the new mLink from mLogic you can now do things with your Thunderbolt enabled iMac, Mac mini, Macbook Pro or MacBook Air that use to be the exclusive realm of big iron workstations like the Mac Pro. mLink and Thunderbolt technology bring the functionality of professional add-in PCIe adapters to these systems...no workstation required.
Another expansion box option for non-Mac Pros. Mlogic lists compatibility with a number of PCIe card vendors, such as Apple, Apricorn, Atto, Blackmagic, Myricom, OWC, and Small Tree. Essentially you can plug in a single full length PCIe 2.0 x16, and access it on any Mac with a Thunderbolt port. The bandwidth isn't there for full x16 speeds, as it's spec'd out for 4x, but if that fits your needs this opens some doors for those not wishing to invest in a Mac Pro.
The MLink is priced at $399 and is expected to start shipping in 2-3 weeks.