Online Surveys.

First of all I should say that some of these do
not pay cash. they can reward you either with
'points' which add up to a voucher with some
online outlet or just enter appropriate amounts into a monthly draw with cash prizes, thus meaning you may not get anything back atall.
So wherever possible go for the paid ones.

What this usually entails is that you register with a site and logon whenevr you want to. On the home page they will show you a list of surveys which need to be completed (it's up to you if you don't want to do them).
You are then guided through a number of pages with questions for which have either 'yes or no' or multples like 'never', 'sometimes', 'always' etc.

Automotive companies may ask you your favourite colour, what do you use your car for and so on.

Each one will be of different length and 'payment'. You won't get much, but it's a little.

Always read the small print and 'terms and conditions' as some may pass your email etc., onto marketing companies and in come the spam and junk mail through the letter box.

There are some good ones out there though and you'll soon sort out who's who.

Articles

If you have a web site, you can write articles and put them into ezine web sites. The criteria is that you have your own signature on them and a link to your web site. This is obviously not earning you money from writing them, but could do if people are looking at your web site on which you sell things.

If you have a strong journalistic slant or can simply write well, you can advertise as being an article writer. Have a web site, or have a page on your web site saying you can write articles 'on the following subjects.....'
You can sell from about £5 upwards for an article. It's getting heard of which is the hardest thing.

Finally, you could even self publish an ebook and sell on the net. Prices vary considerably. The thing you have to watch out for is further illicit reproduction of your work, someone can simply send copies out to all their friends and your masterpiece is gone forever.