See Killer Startup Designs:
Personally I really like: Prestashop and Unbounce.
“Today everyone wants to be a part of a killer startup. You might already have a great idea and it might give you a hope that if it clicks you could be the next Mr.Facebook or Mr.Pinterest. But is it really all about the idea because Facebook was not the first social networking site, neither was Pinterest the first social bookmarking site. Even though there are a lot of things that come into play for a startup to be successful, a major junk goes to the design.”
- Should Pinterest Be Part of Your Small Business Marketing Plan? (paysimple.com)