I'm using CKAN as my open data portal. It's written in Python using Pylons framework. There is an Apps & Ideas page given by CKAN already. It can be accessed via http://data.myckan.com/related. Adding /related to the url will show the page.
How can add this as a menu item to CKAN main menu?
You would need to write your own, very simple, CKAN theme that just has one template that adds a link to the menu. See the theming tutorial: http://docs.ckan.org/en/latest/theming