The Cubix ERS/FT was a great little system at the time. It really improved availability and performance of my cc:Mail system and cleaned up the data center at the same time. Although not quite as flexible as a modern blade server system, the Cubix ERS should go down in history as a worthy predecessor.
Most folks credit RLX Technologies with inventing the modern blade system, but the history of this technology began well before RLX was founded. Companies like Egenera, Cubix, and Sun were influential in the history of blade servers as well.