case-mate and barely there
I've seen the case-mate barely there cases on ebay even before they were released on the official site. As of this writing case-mate does have the barely there cases in stock (at least when I check). It comes in two colors black and pink.
As for the alternatives I bought the Incipio case only because I couldn't resist that thin red profile. But I made the purchase knowing full well what I was getting into--if you are looking for actual protection follow the advice of the previous posters and look elsewhere. It's also worth mentioning that the case-mate version is a complete piece in terms of surrounding the phone--the Incipio has a break on the left side for the charger port and destroys the aesthetic for a lot of people.
On a side note, some ebay sellers seem to be selling the case-mate tough line. I would never personally order anything from ebay without having seen it in stock on the official website. But ebay had the barely there cases even before case-mate's site had it in stock. They did have a preview of the product however, you just couldn't order it. If the tough cases are showing up on ebay it's probably safe to assume that they will be offering it quite soon officially. Even amazon has an official pre-order for the item but their time frame is 1-3 months.
I hope they release the tough cases soon, I had one for the Nexus One and was really happy with it and it looks thinner (by its pics) than the Incipio dual layer case that is currently being offered. I want a bit more protection for my phone but want to avoid making it too thick so the Otter and Trident cases are out the window, even if they offer extra covering.