The first chord taught in the beginner course of http://www.justinguitar.com is the D Chord.  Pretty easy.  Looks like this.

Oh yeah, I know how to read that!  The line on the left represents the string on the top, going all the way down to the string on the right, which would be the one on the bottom.  The “X” at the top of the picture means you do not hit that string when strumming.  The “O” at the top means you strum it as an open string.  Then you place your fingers on the fret where the black dots are.  Now you know the D Chord, too!  You can strum it together, and then pic all the strings individually to make sure they are all clear.