I've read a lot about coffee lately, and it seems to be pretty good with worms- I've heard lots of things about it, from attracting worms to killing slugs and other pests. If you're a big coffee drinker, I think that would be a pretty good start, at least!
(Although some say it's a bit on the acidic side, while others say that roasted coffee is more neutral... maybe try getting some more alkaline materials as well?)
