The lacy ruffled vest: I know, it's a strange concept. But I've been seeing these since summer in Tokyo - on all the coolest girls, and plastered all over the Japanese mags - where girls are using it as a feminine layering peice to tone down the masculinity of all that black, denim, and studs.
And it's super-easy to make!
Cut the sleeves off your top carefully so you leave the finished armhole seams on the shirt. Cut straight down the center of the shirt. (If your shirt didn't have a V-neck before, cut the neck into a V-shape.)
Cut each sleeve in half vertically and spread open.
Place one sleeve on one side of the cut front of the top. (Orient the top of the sleeve cap at the end of the V- of the V-neck; and the sleeve itself centered on the cut CF edge. The sleeve bottom/cuff area will likely be slightly longer than your top length.)
Stitch the sleeve to the top along your shirt's cut edge. (not pictured)
Repeat for the other sleeve - attaching to the other side of the top's center front vertical cut edge.
Cut the sleeve edges into a scalloped pattern - you can follow the pattern of your lace - or cut in a vertical zigzag - or scalloped - it's up to you. It may take a couple tries of cutting and then trying the piece on to see how the fabric falls - and adjusting after that.