Computer Toaster has a helpful article on selecting a Niche Market for Ecommerce (update: the link is now dead so I’ve deleted it) which whilst not written for bloggers has some useful tips on how you might go through such a process of choosing a niche for your next blog. It’s one of those ‘free articles’ – but one of the more useful ones I’ve seen recently if you’re looking for good basic information on this topic.
Update: the link in this post is now out of date – but on the same topic you may be interested to read my post – How to choose a niche topic for your blog.
About Darren Rowse
My name is Darren Rowse and I’m a full time Blogger making a living from blogs like 
Informative stuff; in regards to niche’s to picj what would be the ideal number of searches a month?