Your ads appear in on the search results pages and on websites that use AdSense. You bid on keywords. The more popular the keyword, the more your clicks cost.
If you have a store, this free service is a great deal. Your store will show up on Google Maps, no matter what people search for to get that map. You get a web page too, where you can add a detailed description and add pictures.
This used to be a great free tool from Google, but now they make you pay. You just have to enter in your product description and picture, and it shows up in the Google Shopping search results pages.
Google+ is Google's social network. Their aim is to make sharing on the web more like sharing in real life. I think that if you have a Google+ account set up for your website you will naturally show up at least a little better in the search results.
You put a Google+ button on your site, and when someone likes your content, they can click on it.
Don't forget about the other search engines. Yahoo! and Bing have joined forces to compete with Google and offer pay-per-click ads too.
In addition to Yahoo! and Microsoft Core Search sites, the Yahoo! Bing Network represents a large network of partner sites.
Have you heard of Facebook? It's a social network.
Setting up a Facebook account for your business or website is a great way to connect and interact with your customers. They also offer very targetable ads.
Have you tried selling items on ebay to promote your site? You may be able to get some auction shoppers into your website with your listing. You can get all kinds of information on a successful auction on ebay's Selling Resources Page.
Email Marketing is a very effective way of promoting your website. I've read lots of email newsletters from people who use Constant Contact.
They always look really sharp. It's still up to you to provide the content.
People spend a lot of their time in their inbox. That may be the best place to reach them.