Another interesting tool/service: CloudMagic is a Chrome/Firefox browser plugin that provides enhanced search functionality in Gmail, Google Docs and Contacts. With the latest release they also added the ability to do searches offline, which is a great benefit if you rely on Google services a lot, and also travel. I have not tested the offline side yet, but the search seems to work fine, even though it might take some time to do the indexing, if you have massive amounts of mail. Download from the main page: http://cloudmagic.com/. The release details: http://blog.cloudmagic.com/category/releases/.