At the current time, the best example of Jasig portlet recommendations is the Jasig Weather Portlet. This portlet only provides two main screens, yet provides excellent demonstrations of the use of the following:
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For a demonstration of the use of Proxy CAS from a portlet, please refer to the new CAS Proxy Test Portlet.
Spring also includes a number of helpful sample portlets in each release.
Spring Portlet Development Resources