Here is a useful (and free) website mentioned by Brett on his Cranky Flier blog: the Great Circle Mapper (GCM). The site has recently received a makeover making it more useful and adding a less cluttered interface. According to the Cranky Flier blog, the site can be used for:
- Measuring distance between two airports.
- Seeing how far an airplane can go from a certain city (max range), including various ETOPS restrictions.
- Measuring distances in entire itineraries for frequent flier purposes.
- Looking up airport details and maps.
- Finding aviation weather info (METAR and TAF).
Brett mentioned that he first learned about the site 10 years ago when he first met the site owner and that he has yet to find anything that comes close to what the site has to offer. And more importantly, its free (thanks to the Google AdSense on its pages).