Lots and lots of outdoor stuff :)
I work full-time so no summers off like I used to in school, but I still enjoy the warm weather.
So to answer your question, here's some things that I'm going to try to squeeze in before the end of the summer.
Kayaking trip (multiple if possible), camping trip (also multiple if possible), scuba diving, beach trip to Florida, reading lots of books (I'm a nerd so this comes with the territory), bike rides on the lake, crawfish boils, etc. You get the idea.
The weather here can get pretty hot, so most of what I enjoy involves either water or going somewhere else :)