It is easier to go through a book on a fiery pace. Usually many books have proven examples and that kind of gives you a head start. One of the good ones on Struts is "Struts Survival guide" by Srikanth Shenoy etc(may be I am wrong on the author name). This book helped me become upto speed on the framework and also has many useful tricks and tips. Dan.
The Struts distribution itself comes with a handful of sample applications. Look at each of them to get a hang of Struts features. Look at the tag documentation. And when you know enough, go to struts.sourceforge.net look at the Appfuse and couple other applications. They also have a resources section with links to some online articles Have fun