A.S.
Check out the forum at workplacelikhome.com. It is a great place to learn legit ways to earn money at home, and they even post job leads and can tell you what to look for to see if it's a scam.
If you like to write you can supplement your income at Associated Content. Also check out Demand Studios, Textbroker, and Suite 101, WordGigs, Ezine Articles, and Hubpages.
If you like to blog or want to get into blogging, check the The Niche Blogger program at http://www.thenicheblogger.com/amember/go.php?r=3549&...
You do have to pay to join, it's 19.95 a month but you can have a free trial to see what it's about. I love this program, Amy, the owner, walks you through what you need to do step by step. You don't need any knowledge about blogging or websites to get started. Also, what is great about this program is that you know it works because it is something that she actually does herself. She started 2 years ago and now she makes $5,000 a month from her blogs. Lot's of other people also make a full time income following the steps in her program. I know you said you didn't want to spend any money, but it may be worth considering.
Also, check out KGB or ChaCha.com. Neither will give you a full time income, but it can help supplement your income. These are great because it requires no phone work and you can set your own schedule up.
Check out www.TreasureTrooper.com/minella I made 58$ last month and I did about an hour ever week night while I was watching TV. It's free to do and it's a very easy way to make extra money. I think of it as a hobby that makes me money.
If you have Facebook, check out http://cloudcrowd.com/i/65abd6 They offer tasks for you to do. I've heard it's very easy. I don't have any personal experience with it yet, but I am starting it today. But I have heard good things about it.
There is also Amazon Mturk. It's where you get paid to do simple tasks. It's a great way to earn extra money. If you like to look for products online or help other people find good deals on items, check out IMShopping, you can get money for answering peoples questions.
There are also at home call center jobs, such as West at Home and Live Ops.
If you keep an eye on my blog at www.makemoneyonline.tonoftips.net I will be talking about a work at home opportunity every 3-4 days. I just started it the other day, so I don't have much information on it yet.
If you have any questions about any of this, I would be more than happy to answer them.
Edit: I also wanted to add that you can sign up to test websites. Check out userlytics or usertesting. They both pay 10 dollars per test and take about 10 minutes to complete. I signed up with both, but have only done a test with Userlytics. It was very easy and they paid the next day.