MashUps have a huge potential in the world of web technology where many corporate websites as well as social networks making some of their data available through the use of programming interfaces and RSS feeds.
This hottest Web 2.0 innovation is a hybrid web-integration application that aggregates information from different sources serving a new purpose. A good example would be location, contact and advertisement information of hotels and restaurants integrated into Google maps.
I recommend viewing http://iguide.travel/ and http://radioclouds.com/ to feel the utility value of mashups. Developers can try their wits with free mashup editors like the Yahoo pipes, Microsoft Popfly, Mozilla Ubiquity or even the Google Mashup Editor.