Camelcamelcamel - Easily monitor Amazon product prices and get alerts when they drop.
Anywish.app - Collect gift ideas for your loved ones and share your own wishlists. Add items from any online store. The perfect list maker for Christmas and other events!
Keepa - Price history charts and the option to be alerted on price drops for all Amazon sites.
Gift Hero - The best wish list ever
PriceSpy - PriceSpy helps you save money when shopping online.
Giftwhale - Giftwhale allows you to create personalised wish lists online.