1. American Express Open Forum.
I love this one because it's a network of people who are serious about business. By participating in the American Express Open community you can share advice, blog posts, and answer questions. You can also ask questions. All of these interactions are opportunities to talk about your website and your business. Be sure to share a link to your site as frequently as possible to get the most out of this community.
2. Meerkat
Meerkat's only been around for a couple of month but it's gotten popular fast. It's an app that lets you stream live video from your phone while conversing with your audience over Twitter. By hosting short and interesting video segments you'll be sure to have plenty of opportunities to plug your website.
3. Vimeo
Vimeo is like the high-class version of Youtube. Tons of people go there to watch high quality videos. If you have video content to share be sure to do it there as well as Youtube. Always remember to share a link to your site in the description of your videos.
4. Wikihow
Most of us have some "know how" or expertise. Why not share that expertise with the rest of the world on a site like Wikihow. It will give you an opportunity to educate your visitors about your product, service, or solution and then refer them back to your website.
5. Craigslist
Create a some ads for your products and services on Craigslist. Be sure to include your contact information and specifically your website address. You'll be surprised how many people will see the ad and then just go to your website to get the details or to try and talk to someone.