Word Press ?: Global access control?

Is there a plugin or built-in way to limit people from even looking at a blog created by WordPress unless they're registered?

Answered my own question:
Yes.

This works great and is a very simple solution.

Nice, thats exactly what I needed. Thanks for the help!

Glad it could help. I've been playing with it and the mod does a very good job. It doesn't just protect the home page but the entire blog. I doubt it's going to keep a 12 year old hacker from breaking in, but at least it should turn away the bored-but-curious.