Reviewing on products in your niche is always a fantastic idea. Most people these days tend to do their research online before buying a product so honest, comprehensive reviews on your site will not only give your content but also help in enhancing your reputation within your market. Make sure though that the products you review are related to your niche!
If you're a writer, you need lots and lots on ideas on how to create content prolifically. Your value to your writing clients depends on it... and of course, if you're marketing your own products, you need even more great content ideas.