If your website gets a good number of visitors, there are a number of ways of making money from the traffic. The most obvious way is to use Google Adwords and place Google's double click ads on the site. Google will then pay you for every click someone makes on an ad. The payout per click is usually rather low and it can take a lot of time and effort to attract high-paying ads. Another low effort way to make money from the traffic visiting your website is to join an affiliate scheme and make money from selling other people's products. All the product development and any support still belongs to the original product creator, all you do is get paid a percentage of any product sale you send their way.
The usual way that affiliate schemes work is through tracking cookies. If you place an affiliate link on your website then whenever someone clicks on that link and follows through to the target website, a cookie gets placed on their PC. The user may then download the product - e-book, software application or whatever - and should they then purchase, the cookie will be used to credit you with a percentage of the sales price. Most schemes place a minimum payout limit, say $50, before they issue a check or make a PayPal payment to you. And often, most schemes will only pay out a maximum of once a month.
Finding an affiliate scheme is realtively easy. There are a number of specialized directories advertising affiliate schemes and if you want to sell a webmaster or SEO tool, all the large webmaster forums, e.g. the Warrior forum or DigitalPoint will have a dedicated affiliate section. One recommendation for an affiliate scheme is the SliQ Submitter affiliate scheme. These guys pay 35% commission on all sales you generate for both SliQ Submitter Plus and Lite. If you have a site about SEO, you can easily place an affiliate link and hope to start making some commission on sales. SliQ Submitter V2 is a high speed directory submitter - much faster than even V1 - and hooks into the Decaptcher and Death By Captcha online services to provide fully automatic directory submission options. Two licenses are available - $24.99 for a 3 month license and $49.99 for an one year license. The $24.99 license is particularly cost-effective as it allows you to submit as many websites as you like for 3 months - some other submitters charge a similar amount to submit a single website.