How to entertain baby

My two month old is up for 4-5 hours at a time and keeping him entertained that entire time is hard for me. I don't get much sleep a night so I'm tired and don't have many ideas of stuff to do with him. I sing to him, show him toys and stuff but he gets bored easily and then I don't know what to do. Any ideas? Or what do you guys do with your babies when they're awake for a while?