How about once a week picking a different family from your church to take dessert to? For a couple bucks you can make a cake or cookies together. You never know what a little surprise out of the blue can do for people. Don't stick around, just knock at the door, hand them the dessert, and tell them you just wanted to let them know you were thinking of them, then leave.
Go to a nursing home and read the Bible to someone who can't see to read any more.
Pick one night a week where you teach him something you know how to do, but he doesn't, or something he knows how to do but you don't. For example, teach him a song on the guitar if he doesn't know how to play.
Enter contests. It can be a riot.
Hunt the internet for free samples, and have them sent to someone you don't like.

(ok, I'm joking, sorta)
Learn to dance something like a polka and then go somewhere and make fools out of yourselves.

It's always fun to make other people laugh.