In the Drupal community, the phrase "There's a module for that" is often used and for good reason. Currently the drupal.org site boasts of more than 13,000 modules that have been contributed by community members. Searching this multitude of modules for the ones you need isn't easy, but fortunately taxonomy comes to our rescue this time.
The categorization of modules at drupal.org/project/modules includes a Multilingual category among its options. If we choose that term along with restricting our modules to Drupal 7 versions, then we narrow down our list to only about 50 modules. This is certainly a more manageable number! We won't use all of these in the book, but check out the Appendix, Modules, Resources, and Getting Involved, for a list of multilingual modules we will use as well as additional useful modules. The module list includes project page URLs for all modules, so you will know where to find them.