Usability is of prime concern for startups, especially consumer web applications. It is very crucial that your users find your site easy to navigate and find what you have promised to deliver to them. If the benefits of your startup is easy to identify with and users or consumers need the service you are offering,then user interface may not of prime concern to them. Craiglist is a typical example. These corporate sites have have impresses me.I hope you can find something useful from there. 50 inspirational websites for designers is also a shining example of what designers are capable of. Drawing your customers attention to your site will demand a lot of attention and focus on design. These companies have made a good impression and I will entreat you to check out their designs.