E-bay, (unless you create an online store & really work on suppliers & reliable products), is very good for pocket money, however if you add up the time you take to photograph your products, parcel them up & post them; plus the money to list them, it really isn't that cost effective in regard to monetary return for time spent.

Those online surveys are another example... Many take about 20mins to do and what do you get?  Some pittance or points to go in a draw for something?  Really 20mins of time for the average worker should be worth at least $6, unless a survey is returning at least $5 per time, it isn't really worth your time.  Some that give reasonable returns, (in Australia) are the empowered communications email links... smspup, wdyt, idonate etc.  You only have to click on an email link to earn 1 free sms, 5pts toward a gift card, or 10c to a charity you choose... For the few seconds it takes, they are quite good; sometimes the offers they link to are great value also. 

Toosh mentioned another good one that she found the other day as well, this is called Mylot, there are a few other similar online groups that you can join as well;  I guess it all depends on how much time you have and how much time you wish to spend for the financial return offered.

Some parents on this site will also attest to the value, flexibility and amount of income you can get by doing party plan type sales or catalogue delivery/sales... i.e Avon, Nutrimetics, Tuppaware, Body Shop... The list goes on, there isn't much that you can't buy by party plan nowdays and it is a great way to start out; the only thing that can be inhibiting are the start up costs, though many of these types of companies offer special joining discounts and payment plans.

If you are in Australia and are serious about setting up a HBB, (Home-based Business), then check out this E-business page from gov.business.au.  Visit one of your local BECs (Business Enterprise Centres), to discuss your business idea with a mentor/trainer, this is a free service throughout Australia.

If you have a really good internet connection and some sort of customer service, sales, telephone experience, there are also some reputable call centre companies that offer you training and software to set up and work from home at around $15 + per hour.  You need to be available for about 15hrs per week, advise them of the hours you can work ahead of time & meet those obligations.  Unity 4 is a good example of this type of work, I am sure there are similar companies in other countries that do the same thing.

Family Day Care is another option, check out this site for more information in Australia, a very similar program also operates in NZ.  You receive training in child care etc.  It is a great job if you love kids and it really helps the community by allowing other parents to return to work. 

Once again, I would recommend visiting a BEC to find out how to set this up so that you are getting your maximum tax claims and an idea of the insurance and any other relevant qualifications required no matter what type of business endeavour you wish to undertake.  This is more cost effective than visiting an accountant or solicitor straight up, (remember it is free).

My own personal advice as a mother who is self-employed: Be very specific and honest with yourself about how much time you wish to; and how much time you can dedicate to working and earning money.  Do not over commit yourself as you will not be happy and it  isn't worth earning money at the exspense of time with your children/child.  Try to do something that is reasonably flexible and that you really enjoy; get out of the rat race and get back to basics.  Look for a niche in the community that isn't being filled by someone else, try to have a point of difference so people have a reason to use your services or purchase your products.  If you don't enjoy it  then drop it, life is full of opportunities, being a mum of young kids is a great excuse to seek them out!