This week's book giveaway is in the OCPJP forum. We're giving away four copies of OCA/OCP Java SE 7 Programmer I & II Study Guide and have Kathy Sierra & Bert Bates on-line! See this thread for details.
Jasper reports has an extensive web site, and even its own Wikipedia page; I don't think there's much to be gained by repeating all that here. The reason to use it is the same as for all libraries: because it's easier or quicker than to program all that yourself.