What's a good handgun for home defense?

I've fired a few rifles over the years and have been out to the range with my buddy's Sig once or twice, but I'm far from a marksman. I'm not looking for the pinnacle of modern weaponry, just a solid, reliable handgun for defensive purposes. I'm open to either a new or used gun, and would ideally like to spend less than $400 (although not having a sense of the gun market I would reconsider that price point if it's unreasonable). I'm ambivalent about getting a concealed carry permit (which are easy enough to get in my state), although if it was compact enough for that purpose it would be a plus. What do you recommend?