How to find popular searched topics

Just use Google Zeitgeist or Yahoo! Buzz Index to find popular searched topics.
It does NOT matter if your topic is popular as long as there is a audience for
your topic and the topic is precisely focused then your blog should be
Anything can be considered a niche as long as it has a target audience no
matter how large or how small the audience is.
A blog about your cat can be a niche or a blog about the species of the cat
family can be a larger niche market, if there are people who are interested in
hearing about your cat or the species of the cat family, then you have a niche…
you can even choose to build your audience for a market which an audience
does not exist, but first you must build your blog.