I found this module to be very useful even though it does only one thing -Override text. It is a module that makes it extremely easy to replace text in drupal. With this module you can override any text outputted by drupal. Lets take for example you have a site where you want users to post classified ads. You can easily replace the default text "Create content" with "Post Ad" in one step using this module. Isnt that cool? It sure is!.Download the module from drupal's official website String overrides module.
Install and enable the module. If you don't know how to do this please see "Related Posts" at the end of the tutorial for information on how to properly install a drupal module.
Go to Adminsiter->String Overrides (under site configuration)
Enter the original text e.g Create content and the replacement e.g Post Ad. Click save configuration.

You will notice that "Create content has changed to Post Ad".
**Although this module is extremely useful,i noticed that string overrrides module will not replace text outputted by contributed modules.**