CodeIgniter's got a slew of modules (http://codeigniter.com/wiki/Special:Titles/), but all I can find for Kohana (CI's fork) is http://dev.kohanaframework.org/projects/. Is the assumption that CI modules work in Kohana (or at least can be massaged to without too much effort), or is it just that Kohana's got fewer modules?
Many of Kohana's modules are on GitHub in the following 424 repositories.
This repository (kohana-universe) tracks over 111 modules for you.
The best part about Kohana is that most 3rd party classes and modules can be used within Kohana either with no effort at all or with a simple reorganization of the class structure.
The latest version, 3.0, is very flexible and has very few restrictions on what if allows you to do.
Here's a good place to start: http://kohanaframework.org/guide/using.autoloading
Kohana is no longer simply a "CodeIgniter fork" and has not been for a while so sadly the code cannot be simply copied and pasted across.
Also, CodeIgniter does not have modules, just MVC components, libraries and helpers so I'm not sure what you would be copying from CodeIgniter. :-)