Mash-ups are one of the most entertaining aspects of Web 2.0. It can take many forms and in this post I'll touch on some of them.
I'll start with a predictable one - Google Maps mash-ups. The one most often cited is Paul Rademacher's Housing Maps, a clever mix of Google Maps and craigslist real estate listings. Using Housing Maps, I confirmed for myself just how expensive it would be to live in San Francisco. Another one is Mappr, which uses Google Maps and Flickr APIs to geographically organize Flickr photos. Mappr works by searching for geographic tags within Flickr and adding the photos it finds onto a map interface. It only covers the US and Canada currently, but there are plans to add other countries.
Those are two relatively high profile Google Maps mash-ups, but a blog called Google Maps Mania has links to a ton of them. A recent one with a lot of utility is Google Maps Hurricane Rita Tracker, which is tracking the latest hurricane to threaten the Florida coast via a mash-up between FLHurricane.com and Google Maps.
And if you're wondering how to make your own Google Maps mash-up, Engadget has instructions. Google isn't the only company doing this, of course. Yahoo! has map mash-ups too, as does Microsoft with its Virtual Earth app.
Music has a long history of remixing and with the advent of relatively inexpensive and easy-to-use Web tools for music-making, it's thriving on the Web. For example, The Grey Album was a popular and controversial music mash-up from last year, blending rapper Jay-Z's Black Album with the Beatles' classic White Album.
Just today I listened to a mash-up called "Boulevard of Broken Songs", mixing Green Day, Oasis, Travis, Aerosmith and Eminem. The lyrics blended together very nicely: "I walk this empty street / On the Boulevard of Broken Dreams..." followed by "Today is gonna be the day / That they're gonna throw it back to you...". It was a great remix and it really sounded like an original composition.
OK a lot of music mash-ups are not strictly legal (shhh, don't tell the record companies), but it shows the potential for original and compelling content to be created out on the Web. One can only hope the music industry relaxes a bit and lets people experiment with remixing without fear of being sued.
Other types of Mash-Ups
There are video mash-ups, news mash-ups, software mash-ups (e.g. dropcash uses Typekey and Paypal), blog mash-ups, retail mash-ups and probably many other forms of media have been or will be remixed. The common theme of all this is that people can now use the Web as a platform for mixing together various media and creating something new and original.