Google AdSense and Affiliate Programs
There are several ways to make money from the web. One of the most obvious is to sell a product or service. What if you don't have either? You can make money from the traffic you generate to your website. One of the most common ways would be to use Google's Adsense program. That is when you post other site's Google Adwords on your site and you make a portion of the click rate Google charges. You can currently find them on most high traffic sites, both large and small.
Another method is to sell banner ad space. The amounts you can charge vary but depend mainly on traffic, it's all about traffic. Collecting an email list is a great way to prove your client base to potential advertisers. You can also go through a company like Commission Junction that already has relationships with hundreds of advertisers. You can select relevant ones to show and make a percentage of each transaction that originated from your site.
Yet another way to monetize your site is to sell products through affiliate partnerships like Amazon Associates. You are able to set up small widgets, mini storefronts or complete Amazon storefronts skinned with your own website design. Typically you will make 4% of each sale.