How about work with natural language?
Even with all sorts of modules, handling natural language is something huge. You could set a small goal to improve a piece of functionality in that area. For example, search engines. I put in the phrase "Is there a site where I can obtain pearl modules?"
work on code which through a bit of intelligence and a bit of brute force realizes I typo'd and what I want is computer related PERL modules and not a module for a pearl or a module made of pearl.
There is so much that can be done with natural languages it can make ones head spin just trying to grok it all. The only problem you might run into is biting off more then you can chew for the scope of the project.

thanks,
2501