Well, you are right when you say niche is important when you want to monetise your blog. Creating content that is mostly in demand would be best way to get better income.
A few good niche from the profitability point of view would be -
1. Medical and Health care
A health blog can cover many points such as fitness and nutrition. You may also go for weight control, diseases or health research. It has been proved beyond doubt that health niche is the number one option when it comes to getting better income from blogs.
Technology is another hot selling niche from the profitability point of view. You can keep providing useful information on latest gadgets and technological advancements.
You may also consider providing tutorials for resolving the common issues concerned with the technology and gadgets. Please note that the niche has not been saturated even with a huge number of blogs depending on it. However, it would be important to note that the blog will need constant updation to stay ahead of competition.
Yes, blogging on blogging is another great niche. With the high number of bloggers on the rise, there is a constant demand for the tips on how to blog. So, why not start a blog on blogging itself? Most of us have issues with our blogs. Pay attention to the tutorial part as it would be more apt.
If you are an expert in HTML tags, SEO or any such fields, share your knowledge. Sharing is caring, they say. Sharing is earning , let us prove.
4. Money and Business
There are a few blogs available in this niche, yet it is still in demand. Share your ideas on how to earn money online or offline. Needless to say - stay away from suggesting something illegal.
Business niche needs an expertise on how to start a new business or run it. Share tips from real life stories so that you will look realistic.
5. Home Decor/Crafts
Crafts and do it yourself sites attract much traffic these days. The niche has the huge potential to be the best money spinner. Studio DIY is one of the examples for a successful blog.
Live....and Let Live!