All of mine where whilst I was at school from about 8 to 14...
Normal job as a door to door catalogue salesman/order taker/etc, but got it from some weird bloke driving around looking for people to do it... all very suspect looking back at it now. Did it once then quit as nobody had actually signed up to have the catalouge and were all quite rude to me asking for them back.
With the advent of the 16-bit home video game consoles and better background music (one step up from bleep-bloop) a friend and I would record the music, remix a bunch of them (badly) and make tapes of the result to sell to people at school. I think we sold about 3 tapes after putting in about 50 hours of work and needing about £150 worth of kit, so we ended up earning about (minus) £2.95 an hour! :)
I also used to collect all the little ali bottle tops to try and sell to the local scrap metal man - after collecting a rather large ball of them for several weeks, I got 50p, and I think that was just because the guy took pity on me.
My uncle had a vast collection of comics he would give them to me after he was finished with them. After I was finished with them I would "rent" them to friends at 5p a day and 10p to join the club - this one actually worked quite well and I made about 20p a week.
I wrote a computer game and sold a few copies - this one seemed pretty good until I realised I'd spent about 200 hours making it and only made £9 off it - a lot of people just copied it and I learnt the harsh lesson of copyright theft!
The best I manged was when I wrote a bit of software to make those magic eye / 3D stereo scopic pictures. This time I learnt my lesson and took orders for pictures instead of selling the software I sold the pictures. The software took about 10 hours to make and about an hour for each picture I made. I made about £100 from the picture orders. If the internet had been around, I think I'd have made more from that one!