Microworms are pretty much completely useless unless you're raising very small egg-layer fry, since the worms are almost microscopic and too small for adult fish to eat. In addition, they apparently are not as nutritious as baby brine shrimp so they probably should not be used as a stand-alone fry food (but they sure are a lifesaver if your BBS hatchery fails one day).
What kind of fish are you interested in feeding? Some larger types of easy-to-culture worms, in order of size, are grindal worms, white worms, and black worms. If you do a quick Google search you can find information on how to culture each of these, as well as places to order a starter culture online. Alternatively, there are probably forum members with worm cultures going who might not mind popping a starter culture into the mail for you. I'd offer, but my cultures are infested with fruit fly maggots and some weird little soil mites, so I doubt you'd want that.