Well, rubber is in fact recyclable strictly speaking, but you would need an awful lot of them to make it worth anybody’s while. Some people may even say it’s compostable given that it is originally made from a natural product, but the processing it goes through to form it into products can make it very slow or even impossible to decompose.
The best advice therefore is to reuse them if you can!
The other option you have, especially if your main source of rubber bands is the postman, is to return them to the Royal Mail. Chances are your postman will take them back for you, or you could send them FREE OF CHARGE to :
Royal Mail, Rubber Band Recycling Department, Freepost, Tomb Street, Belfast BT1 1AA