How to make spare cash online

Associated Content 
Fancy yourself a wordsmith? With the help of Associated Content, loquacious writers can make some extra change by selling their daily musings online. The site accepts all types of media, from text to video. Topics are similarly diverse ranging from laptop reviews to dieting tips. Once your submission is accepted, it's either posted on the site or on one of Associated Content's partner sites. Not sure what to write about? The site posts daily "Calls for Content," letting writers know specific subjects that are needed.
Pay Scale: Associated Content pays about $1 to $30 per article. (Article length varies.) In addition, you can earn revenue from your most popular stories based on its page view count (you receive $1.50 for every thousand page views.)

Amazon Mechanical Turk 
You may not surpass Jeff Bezos' salary, but if performing small tasks on an hourly basis is your idea of fun, you might like Amazon's Mechanical Turk. The site pays freelancers for performing "Human Intelligence Tasks (HITs), which require anything from writing translations to copy editing. You choose the HIT you want to work on and upon submitting and approving your work, the HIT requester deposits your pay into your Amazon Payments account. The HIT requesters are companies looking to fill their websites with unique content. For instance, at the time of this writing, FriendsEat.com was paying $4.51 for 20 short restaurant reviews. Write more than four sentences and the pay jumps to $4.55. Many of the HITs you'll find are monotonous, but they're relatively easy and there's a healthy mix of low- and high-paying HITs to be found.
Pay Scale: With HITs that pay from $0.01 to $7.50, Amazon Turk will buy you the least amount of beers.

Google AdSense 
Want to make money off your blog? With Google AdSense, you can. This online ad service places targeted ads on your website and pays based on the number of visitors who click on the ads, or cost per thousand impressions (CPM). Since you're in control of your blog, you can write about whatever you want. Google in turn will try to match your content with the appropriate advertising. When someone clicks on one of the ads, you get a portion of the money that Google collects.
Pay Scale: Unfortunately, pay for this model varies greatly and is dependent on how much traffic your blog gets and the amount of money your advertiser is paying. While some people have reported making upwards of $1M a year, sites with low traffic can expect to earn around $100/year.

About.com Guide 
Though it requires the most commitment, becoming an About.com Guide offers the most potential to earn cold, hard cash. The New York Times-owned site hires freelancer writers who are well-versed on specific topics. (Topics can range from digital cameras to scuba diving.) It's then up to the freelancer to maintain and update About.com's page on that topic. Rookie guides must publish four articles every month with gaps of no less than 14 days between articles. In addition, guides must update their blog one to three times a week. You can work as many hours as you wish, but your work is edited and could be subject to revisions.
Pay Scale: According to About.com, new guides average about $1,000/mo. for their first two years. As your content and page views grow, some guides can make up to $100,000 a year.

Conclusion
Keep in mind that, the amount of money you make on these sites is usually proportionate to the amount of time you're willing to spend. In other words, working at these sites won't turn you into the next Internet millionaire, but a few extra dollars in your pocket never hurt anyone.