This is one I've personally tried and found it to work pretty well, what it consists of is completing a fair few surveys and usually getting money in vouchers to spend online. In the past I have received Amazon ones which can be quite handy, especially with Christmas coming up. I know that a lot of people find doing surveys annoying as you have to do a fair few to make it worthwhile but it can be an easy way to make money.
Write an E book:
I have seen this pop up a lot more regularly, and if you have a talented which others can benefit from why not sell it on Amazon/Kindle I know of bloggers who have made books on blogging which is pretty amazing, not only do you benefit from some amazing content, you also help a fellow blogger.
Get cash back when shopping:
This is one I need to start doing as I am forever online shopping (oops), I've heard from several bloggers that it is an amazing way to make money. Every time you shop a certain store, they give you a certain percentage back in cash back on the websites I looked into like Quidco and Top Cash Back you can earn up to 10% on one purchase, now that's pretty sweet.
I am aware this one isn't for everyone, but others really enjoy it. With lots more things going online every year than ever before that includes different formats of online gambling such as slots and bingo. You never know you could put a little in and get a lot back and some sites even offer a free game or two. I've also come across free slot sites recently, which are amazing for fun and also gaining money.
This one involves a lot more effort than the rest, but great if you need a good clear out. Selling your old things which you no longer need such as clothes and CDs is a great way to get a little money in your back pocket. There is also other sites than just Ebay, like Depop and other equivalents.
Sell Your Services Online:
Now this a lot less dodgy than what it sounds, what I mean by this is selling your skills online to customers who may struggle in that field. For example, making web designs for small business owners, or writing an article for someone. It is usually lower pay than what you would get in the real world, but it is great to make a few extra quid and some people make a lot of money.