Don't Use Tags & Clouds in Your Sidebar 

Although most would not recommended this, it is one true sign of a blog vs. website. Tags do provide SEO benefits, helping Google and blog directories find and categorize your site.Just keep them off of your sidebar. 

Speaking of Your Sidebar….

The key here is to have it be consistent. Titles such as Blogroll, Categories and Archives are blog related and your visitor will immediately identify your site as a blog. Also, keep an eye out for themes that have different sidebars depending on the page that you are on. Keep it simple, keep it consistent.

More on Your Sidebar….

By displaying and using your Pages in your sidebar, you provide easy navigation to your site and also the look/feel for a website. Use the “Pages” Sidebar Section as Your Main Navigation. How to do this varies on the theme that you are using. Some provide the Pages already in the sidebar, while others allow you to insert it via widgets.

Use Nice Search Plugin 

It's a great and simpleplugin, making searches your visitors perform on your website look less WordPress-style. It gives the look of a customized search engine that has been installed on your website. 

Don't Use Comments on Your Pages 

User-contributed comments are a easily recognized as being part of blogging. Keep your comments limited to your Posts, but disasble them on your Pages.

Towards the bottom, in Discussion, make sure that Allow Comments is disabled. This will give your site the atmosphere and feel of a website. 

And Most Importantly… Don't Refer To Your Website as a Blog

If you want your site to be seen as a website and not a blog, don't refer to it as a Blog. Probably the most simple and yet most commonly overlooked tip!