Writing articles is a nice little way to make some extra cash. If you like to write, you can be paid for your articles or your opinion. A basic way to do this is by joining a pay-to-write site such as Associated Content, Constant Content or My Lot. You can choose a topic and write about it. Then you can submit the article for payment approval.
Different sites work differently. Some sites will pay based on the value of the topic you choose or article length. Some sites have content available to be purchased by others and you're paid when your articles are purchased. This type of writing gig varies greatly in requirement and pay. You can make as little as $3-$5 for a simple article to $20 or more. It's not high paying, but it's a great way to get your foot in the door.
If you're a little more experienced in your writing, you could consider writing an ebook to market and sell. Ebooks are great because you can avoid the cost of not only creating and publishing the book, but shipping costs are also nonexistent because you're sending it via email or download. One simple way to market an ebook is to find blogs that are compatible with your subject matter and see if the blog owner might be interested in being an affiliate to promote your book for a percentage of the profits.
Some companies will also pay you to post on messageboards. One company that does this frequently is Paid Posting Tools. You choose the subjects on which you'll create posts or add to conversations and you're paid a few cents per post. Typically a certain number of posts are required per week and they can start to add up to a decent amount of income.
There are much more lucrative ways to earn money writing, but these are just a few to get you started. Writing is another great work-at-home activity that can easily be done on your own time, without a set schedule or a need to get into the office. It does require quiet, non-kid time, but it's definitely something that allows you to start small and grow bigger as you want to.