Mashup madness is sweeping the web and you too can be a part of it! Start small, have fun and be creative. Below are some resources to get you on your way to creating your own mashup masterpiece!
The Ultimate Mashup Glossary - Ultimately the best go-to guide for mashup terms.
Google Maps API Code Cheatsheet - A visual example of what code should go where.
Mapdango - An extensive Google Maps mashup that lets you explore locations with helpful information including weather (WheatherBug), photos (Flickr), facts (Wikipedia), events (Eventful), news (Google News) and more!
Cost2Drive - Accurately predict the cost of gas on any road trip. Combines local and average gas prices with google maps and vehicle-specific MPG data.
CrimeReports - A Google Maps mashup that lets you search crime reports by location in near real-time.
FundRace 2008 - A mapping mashup that lets you search by name or address to see which US presidential candidate your friends, family, co-workers, and neighbors are contributing to.
WikiMapia - A mashup that combines Google Maps with a wiki system.