There are many other niches and topics that can be equally as popular. Stephan Pylarinos has a list of 141 popular Kindle niches to help get you started. There is literally a topic for anyone who is interested in writing an eBook. Don't be afraid to use your own expertise and experience to write a unique eBook. Sometimes the best sellers are ones that have a sense of authenticity and genuineness about them that resonate with readers.
Other ideas for eBooks: