More and more companies are doing jobshare options now, which might be worth looking into. A school is an obvious choice of course.
Other options - look at your skills. Can you bake, write beautifully, make jewellery, iron well? Can these be put to commercial use? What about looking after pre-school children?
Selling on ebay is easy and can bring in good money. Mystery shopping is great fun, and freelance - you do it as and when you want to, and as much or as little as you like. If you decide to go down the mystery shopper route, I would suggest signing up with a few companies, as they offer varying amounts of work. I did mystery shopping part time for years, I still do some even though I work full time.
If you are interested, try googling for 'Gfk NOP', and TNS. I've worked for loads of companies, but those 2 have been the best by far. Most of my work comes from Gfk NOP, but TNS jobs tend to be more fun - restaurants, bars, hotels etc.
There are lots of options, it just takes some creative thinking!
Good luck.