My verizon router came w\ a sticker on it w\ the default WEP key.
If you can't find yours, you could always reset your router. There's going to be a reset button on the back somewhere. Hold it down for 10-15 seconds, then release. It will reset your router and you will need to go in and set up security so it's not wide open.
most routers are 192.168.1.1 login : admin /password. some are different, the linksys wrt54g is blank user name, admin for the password.