When I was living in Paris my friends and I were all registered with some marketing companies that used to call us occasionally to invite us to group discussion regarding a new brand of biscuits, no to taste it but to talk about the packaging, the quotes used in the advert etc. For all these sessions we were paid about £40 to £60 just for 2 hours.
I also tried a new gel for L'Oreal and a friend recently went to Senegal to comment on a holiday resort.
We also used to go to the theatre for free because a gay ticket brokers arranged to fill the room of gay pulic the first weeks of performance so that the word-to-mouth would sell more tickets in a long term.
Here in London it seems that it's the other way : you pay for everything, you never (rarely) get something for free and of course you won't get paid to do something.
A few weeks ago the METRO free newspaper was giving 3 tips to make extra money (and have fun), so I registered to the first one, we'll see if I get called.