Depending on where you are, if you wanting to actually recycle them (that is, not try to use them for anytyhing else) there is a company in the UK called "Polymer Reprocessors Ltd". You can find a link to their website with a video on what they do here. A good thing to note is that they recycle them in an environmentally friendly way. Another thing to note is that you do have to pay postage, but at least you can know yourself that you are doing your part to save the planet.
Other alternatives (if you are interested in using them for other things) are creating things such as this or this which could be quite fun.
Other alternatives (if you are interested in using them for other things) are creating things such as this or this which could be quite fun.