Of course many of hte offerings are focussed at WebSphere, but the third party vendors are creating JSR168 portlets that can run on any platform. It may be a good start.
Good luck on your quest.
The WebSphere Portal Catalog describes the offerings that are available for the WebSphere Portal products. These offerings are created by IBM and IBM's Business Partners. The catalog enables you to search for information that meet specific criteria such as:
* Portlets and portlet builders * Tools and other applications which integrate with WebSphere Portal * Solutions, such as services and value-added offerings
You can browse through the categories in the catalog. Each catalog entry contains information on the function as well as pointers to additional information about the offering. You have access to the provider's Web site where you can learn more about the offering, and you can use, download or license the offering.