There is a lot of discussion around how to develop portlets using Wicket.
If you download a Wicket distribution package, there is the "Wicket Examples" webapplication WAR enclosed.
This package is not only a webapplication, but can also be deployed as a (collection of) portlets.

Here is how to run the examples as portlets:

Liferay

Deployment

After deployment you can see the Wicket portlets listed:

Usage

If you want to use a portlet in a page, follow these steps:
(* Create a page: "Add Page"-Link)

Problem: Portlet does not show up...
Solution: This might help: http://issues.liferay.com/browse/LPS-1911