Users in the Google Earth forum often ask about the age of satellite imagery and when the content will be updated. To, be able to tell you in advance when the imagery will be updated, Google introduced "Follow Your World application," you can register points on the globe and we'll send you an email update whenever the imagery is updated there.
In just three easy steps, you can add points such as your hometown, your college football stadium, or just about any place on Earth. And since Google Earth and Google Maps share the same imagery, this tool is equally handy for enthusiasts of both products. Follow Your World also provides a handy dashboard to manage your subscriptions.
More Info: Follow Your World
"Simply use the app to indicate areas around the world that interest you - be they your current neighborhood, college town, or dream vacation spot - and receive an email update whenever new satellite or aerial imagery for those places are added to Maps and Earth."
Update 10/20/2011, Google just announced the expansion of Follow Your World tool, which is now localized into 43 additional languages.
Arabic, Basque, Bulgarian, Catalan, Chinese (Simplified), Chinese (Traditional), Croatian, Czech, Danish, Dutch, English, English (UK), Estonian, Farsi, Finnish, French, Galician, German, Greek, Hebrew, Hindi, Hungarian, Indonesian, Italian, Japanese, Korean, Latvian, Lithuanian, Norwegian, Polish, Portuguese (Brazil), Portuguese (Portugal), Romanian, Russian, Serbian, Slovak, Slovenian, Spanish (Spain), Spanish (Latin America), Swedish, Thai, Turkish, Ukrainian and Vietnamese.