I just bought a domain, but now that I have it I need a host..right?? Yeah, I'm a noob.

Right, you need a host and a domain. A domain is an address that points to your host; often you can get hosting and a domain from the same company, but if not, you just need to point your domain to your host.

You can also host yourself, but that's unreliable unless you have a fast, always-on Internet connection with a static (unchanging) IP address.

I bought the domain with Yahoo, but their hosting is way to expensive. It actually kind of riduculous. So, where can I get cheaper web hosting?

This thread lists some webhosts.