By far the two best places to learn and ask questions about the Struts framework are the two mailing lists, STRUTS-USER and STRUTS-DEV. The user list currently has around 1,750 subscribers and has been growing at a rate of 50 to 100 new users a month for the past year or so.
The STRUTS-USER list is designed for Struts developers, both new and experienced alike. You definitely should consult the FAQ (http://www.tuxedo.org/~esr/faqs/smart-questions.html) before posting any questions. There's not much flaming on the list, but you will get pummeled if you don't think about the question you're asking before posting it.
The STRUTS-DEV mailing list is devoted to those working on the framework itself. Anyone can post on it, but you should not ask questions here about your application, or questions that can be better answered on the user list. In almost all cases, unless you are contributing to the development of the framework or bug fixes, or would like to get involved in this manner, you should be posting to the user list.
You can subscribe to either or both lists from http://jakarta.apache.org/struts/index.html#Involved. There are also several ways to search the lists (you can search through many Jakarta mailing lists, not just the ones for Struts). One option for searching the Struts mailing lists is to go to http://www.mail-archive.com/index.php?hunt=struts and select whether you want to search through the DEV or the USER list.
Another way to search is to use the eyebrowse feature from the Apache Software Foundation (http://nagoya.apache.org/eyebrowse). You can search through all of the Apache mailing lists here as well.