Many online writers use writing sites to supplement their income. Those sites pay usually either a share of ad revenue, an upfront payment or a mix of the two. There are many sites that only pay US citizens, but some also pay outside the United States, provided you have a Paypal account or can open one. The following are my favourite freelance writing sites and those in which I am active at the moment, and they all require a minimum of 400 words articles average so they are not just short bookmarking sites. The ones that allow you to place links offer do-follow links and can be used to complement your article marketing strategy while making some money on the site.
Wikio-experts is a french based writing website paying in euros, which makes it a great option for Europeans. They offer articles with upfront payment of up to 8€, or a mix of ad revenue and upfront payment of up to 15€. The articles need to be short, around 450 words maximum and while every article is reviewed by an editor they don't demand you to cite sources for everything, even if you wrote from your experience. You need to write to their titles and format specification, but there is a good variety of available subjects. Despite the apparent lack of buzz about its english version, Wikio-Experts is not a scam and the original site in french is very popular. However, don't expect your ad revenue earnings to amount to much as it's still quite unknown.
Infobarrel is an Adsense share revenue site that offers up to 90% of impressions as your share, along with do-follow links and editorial control to ensure your articles aren't surrounded by spammers writing spinned text. They also allow affiliate links, up to a maximum of two self-serving links on one article. They pay directly into your Google Adsense or Chitika accounts, so if you can open either of those you can make money at Infobarrel.
Hubpages is another Adsense revenue share website that pays anybody who can open an Adsense account, but recently they have opened their own Hubpages Ad program that pays for impressions instead of clicks, through payola. This makes them a great option if you like using pictures and media on your articles but you don't usually get many clicks. They are also enforcing strong anti-spam policies, but some hubs are still spammy or written in pidgin english.
Demand Studios commissions articles for sites such as eHow, following strict editorial guidelines and requirements for about 15$ per article. They offer regular work and a large variety of subjects that are created from long tail keyword searches, and there are people making a living off Demand Studios. You can also take part as a video author.
Squidoo is similar in format to Hubpages, but doesn't require an Adsense account. Instead Squidoo pays you every month depending on the lensrank of your lenses, quite a complex algorithm that factors things such as traffic and affiliate sales made through your lens. You can use your own affiliate links and they also offer Amazon and Etsy affiliate modules as well. Their spam filters sometimes are too strict, but the community is really friendly and helpful.