The unstructured blazer is a must for the warmer months. I love this double-breasted one from Banana Republic. The double-breasted design, paired with peak lapels gives it a more unique look that can easily be dressed up with a dress pant and tie, or thrown on with a tee shirt and jeans. For around $300 (or $190 if you get it during their random sales like I did) its hard to beat. For this look I paired it with some light cotton chinos, and some double monks from Cole Haan.
Watch: Victoninox Swiss-Army, Pants: Jcrew, Blazer: Banana Republic, Tie: Bows-n-ties.com, Shoes: Cole Haan, Shirt: Brooks Brothers, Pocket Square: Cotten Brew.