Yes, I'm aware of that strategy but wouldn't it be effective if you could input a keyword and a tool could come back with the websites that have the most traffic relative to that keyword. Any other ideas?
How are you searching, londrum? I see CNN, ABC, Fox and others on a search for "news", Barack Obama (i.e. whitehouse.gov) for "white house".
Even with Alexa, though, you're only seeing the sites that they think are most relevant to your search. The data is incomplete, no matter what tool you use.
If you're serious about entering any niche, then getting to know the bigger players is step 1, and it really shouldn't be too hard to figure that out. I certainly wouldn't rely on any third-party tool to give me those answers though -- that would be careless, lazy. You can't reasonably expect to compete when rushing it.