A very minimal D7 Postal Code (ZIP Code) field with validation for one country (listed below) or a combination of countries.
Countries with validation:
To configure this module, navigate to admin/structure/postal_code. Selecting countries in the 'Valid "Any" Countries" list will validate the submitted postal code against regexes for those countries using the "Any Country" widget type. If you want submissions validated, make sure to check the "Validate" checkbox.
To configure content types to add this field type, navigate to admin/structure/types. Select "manage fields" beside the content type (eg: blog, page, article...) and follow the normal procedure to add a new field, choosing "Postal Code" under field type. Beneath "Widget" a number of selections will appear for each country type, as well as an "Any" country which is configurable (see above) to validate any included country's postal code.
Difference from postal_code_validation Module :
Module "postal_code" provides a feature to create a field of field type postal code with different Field API widgets such as 'Postal Code:Any Format,Postal Code:Canada Format etc'. And there is a configuration form(admin/structure/postal_code) where we select countries to be validated if selected widget type is 'Postal Code: Any Format'.
Whereas "postal_code_validation" Module provides a validation function which need to be called on #validate attribute of a custom field when building a custom module with country code and data as parameters.
Note: If you wish for a specific postal code or zip code to be added to the module, please add a ticket to the issue queue, not the bug queue. The issue ticket should contain the name of the country to be added and the regular expression for validating the code.