These are in order of which ones I think are coolest:
Isillon - I know we have some at my current company, and they work well. Nice product, no idea on costs.
Onstor - Seen these guys when I was looking at 3par, product looked good, cheap, and solid.
Netapp - old faithful is something thats good with storage :) Easy to find people who've used it. Who hasn't?
Bluearc - seems good
Ibrix - Looks interesting since you don't need to buy hardware, but might be too "out there"
Pillar - looks okay...