With locate you can quickly find all files containing a given string. For example, "locate project" lists all files whose name includes "project". However, before you can use locate you have to build the index used by this command. For more information, see here.
Such search tools enable you to easily find documents, emails, instant messenger conversations, notes, source code, images, etc. Besides the source code, binary installation packages of Beagle are available for most major Linux distros and can be downloaded here. Recoll downloads are available here.