If you're interested in writing book and movie reviews there are many opportunities online.
First, you can write book, movie, and music reviews at Amazon.com . Amazon.com does not pay for these reviews. But you can consider this a website to write practice reviews while you are learning to write these reviews.
For paying websites, of course, we recommend Triond , Associated Content, and Constant Content.
You can also write reviews at Shvoong.com.
Shvoong is a revenue sharing website. Another revenue sharing website is Reviewstream. In addition, if you are an Associate of Amazon.com, if book, movie, or music is ordered via your review then you receive payment via Amazon.com.
You can also write book, movie, and music reviews on your own website or blog. If you sign up as a publisher with Google Adsense then you can earn revenue on these websites.
If you're are interested in publish book, movie, and music reviews in the newspaper and magazine print market, then you should maintain a portfolio of these online reviews. You can send copies of your portfolio with any queries to write reviews for these print markets. Some might also be interested in reprinting your online reviews.
You can also collect your book, movie, and music reviews reprinting them yourself in books and ebooks, published at Lulu Press or Cafepress. Again, these self-published works can be submitted to commercial publishers for reprint. You can also organize these reviews into a book around themes. For example, you might review movies in which science is a theme and/or movies in which scientists are central characters. This might make an interested book idea for commercial publishers. A collection of rap or jazz music reviews might also be the central theme for a book.
These are just a few of the ways of starting your career as a book, movie, and/or music reviewer making use of online publishing opportunities.