Here's what I've found.
There's a new type of case called TPU (Thermoplastic Polyurethane) that offers optical clarity of a hard plastic case while being extremely flexible. You can find a bunch of choices on eBay. I've bought an Epik case in black and matte, a choice that's not available outside of eBay. It should be here soon.
I've also found on eBay a bumper style case (black rubber surround w/ a clear plastic back), supposedly made by Luxmo. It'll be here soon.
Case-mate just released a Pop! case for the Thunderbolt.
HTCPedia.com offers HTC branded case, along with Verizon cases.
Verizonwireless.com also offer a dual layered case, with an inner silicon lining and a hard plastic outer.
BTW, Otterbox hasn't released any design yet.