I found a build I like, it's called Half-Orc Shock Trooper. There is a list of feats and powers but with no description or source. Where can I find out in which book or magazine are their descriptions?
The easiest thing to do to find the source of a feat is to search the WOTC online compendium. You have to have DDI to get the power/feat etc text. But the search helpfully lists the source for it so you can go find it in a source book.
The D&D Compendium http://www.wizards.com/dndinsider/compendium/database.aspx will show you what the source of the feat and/or power, but it unless you sign-up for the paid version, you will not get the rules text.