I use A*s Sniper Air-Flo Mesh jacket. Great for the just the summer. Most of the construction is mesh, so it lets in good air. Its not a good early spring/late fall jacket because there in no removable liner or zip mesh panels. The only panels that arent mesh have padding or CE armor behind it. Even then that material is light. And I bought the white one, so its much cooler in the sun than the black one.
http://www.alpinestars.com/store/pro...id=330288&cs=1