Useful and fun apps on mobile phones

Don't you always wonder users visiting site xyz(eg: wikipedia.org), what other sites these users likely visit as well? By using the data from Google Trends for Websites, our website discovery tool lets you visualize a 2-degree social graph/connection of a web site(think Linkedin for website, but the connections are directional instead of bi-directional).
Cooking skills used:

• Ruby on Rails for the backend
• Adobe Flex, BirdEye visualization library and Yahoo's Flex skin for the UI.

This was the idea that we had during one of our iPhone application designs. Won’t it be cool to draw iPhone application ideas/UI directly on a Post-it that looks just like an iPhone? And we made it!
Cooking skills used:

• Spree - Open Source E-Commerce for Ruby on Rails
• Amazon Web Services for hosting: the whole site is hosted on Amazon EC2, and the data is on Amazon Elastic Block Store

Let users embed a virtual voicemail box on their websites, social networking profile pages and blogs where they can receive feedback, questions, or ideas via voicemail from your website. Cooking skills used:

• Ruby on Rails
• Adobe Flex
• Integration with widget distribution platform Widgetbox