Check yours and post in comments :)
I've got 4 of the damn things (usually forget it) and with £5 on each one minimum (what you pay for one at the machine/kiosk) plus whatever value you have on them for travel can be claimed back.
A lot of people use these in the summer holidays for one or two trips to sunny London / Outer London, well worth getting your cashback rather then sitting in TFL's pockets.
How do you claim? well, here's how.
Click on the ‘Oyster refund’ option and then follow the onscreen prompts.
You will then receive the cash via the machine (YAY) BUT once you've claimed the money back your Oyster card becomes void and cannot be used again.
You won’t able to use ticket machines for a refund if you have a season ticket.
Your card will need to be registered first (see get deal link) and then you need to select ‘apply for a product refund’ once you have logged in.
Your remaining season ticket, credit and deposit will be refunded.
The Oyster card would be again be void.
Phone TFL customer services on 0343 222 1234 and give them your Oyster card number and security question answer, they'll then go through the steps and you'll get your refund.
Again your card will become void.
If you want to do it the snail mail way
Send your Oyster card to the address below and ask for a refund:
TfL Customer Services
14 Pier Walk