i've been doing a number of things personally...
do you have any old mobiles phones? if you do, sell them - there are loads of companies like mazuma or mopay.co.uk... it's worth shopping around to see who offers the best price. If you have a local CEX store near you, you can always take it in - i wouldn't recommend sending it as i had a bad experience of sending in a practically new phone and they 'graded' it as a damaged phone... couldn't get hold of them on the phone at all and offered me just 10% of the phone's value.. but if you take it in to store, then at least they can't argue.
if you're really strapped, then you could sell gold? there are envelopes at most whsmiths stores for this, however note that the price they pay is probably about 60% market value...
matched betting is something i've been doing recently - its where you take advantage of incentives given by bookmakers and is considered risk free.. google it, there are a number of sites that talk about it. i've been using fixtheodds.com which is a good starting point - made over £65 with them so far..
mystery shopping - have you tried signing up for any mystery shopping websites? i've been doing Aba-i.co.uk, who have sent me to wilkinsons and harpers bazzar for 5 times now - that's £10 each time so i've made £50 from them.. it's fun too and really tests your memory!
if all fails - do a car boot sale!