My summers are too busy to brew so I load up the bottles in the winter. I bottled a pale ale today and next week I have a blueberry and a spiced dark ale to bottle. Then I'm thinking about a blond to brew.
I brewed a berlinerweisse using the method in Zymurgy. Turned out fantastic! I really can't imagine a better beer in the summer heat while mowing the lawn. Slightly sour while crisp and totally sessionable (3.5%). No matter what you brew, it will be delicious because it's yours!
I make the Belgian Grisette from Farmhouse Ales (a small saison--think Ommegang Hennipen) and add a portion of oats to the grain bill. It is fantastic for summertime, and I tend to brew with the seasons so the WY 3711 can cut it in the heat of Texas.
Summertime also brings on Hefeweizen, Dampfbier, Kolsch, and Gose.
I don't have my recipe in front of me, but I just use 1 lb of Lyle's Golden Syrup (turbinado would be a fine substitute) plus enough Golden Promise malt to get me to an OG of about 1.045. Bitter to about 30 IBU with a combination of Fuggles and EKGs added in the first half hour, and then add Styrian Goldings at flameout (I use 1 oz for a 5 gal batch). Ferment with Wyeast 1469 (should finish around 1.010 or slightly under), carbonate to 1.5-ish volumes, and enjoy the goodness!
A couple of IPAs, a couple of Kolschs, I want to try a swarzbier and lager it all summer to drink during football games this fall. Also thinking about a bacon porter. Maybe a Mexican lager. Who knows? I'll just do whatever I'm in the mood for when I'm at the LHBS.