AmzScope - Find profitable products for sale on Amazon in one click, relying on statistics instead of intuition
Savelist - Found products you want but not ready to buy?
Jungle Scout - Amazon product research made easy.
Camelcamelcamel - Easily monitor Amazon product prices and get alerts when they drop.
AMZScout - AMZScout extension will help you make a decision about picking a niche based on the actual data, not intuition.
LoveSales - Find and save products you love, get alerted when they go on sale.