Camelcamelcamel - Easily monitor Amazon product prices and get alerts when they drop.
Guides by Lonely Planet - Explore city guides curated by experts.
Fetchee - Fetchee is a free price tracking wish list app that works with all online stores worldwide.
Flamyngo - Create a city guide with help of your friends.
Keepa - Price history charts and the option to be alerted on price drops for all Amazon sites.
Foursquare 10 - Your ultimate city guide, in your pocket