What kind of beer can I brew in the summer (30C by day, a few less by night), without special cooling equipment? Anything special (but not too complicated/expensive) I should do?
Saisons are great warm temp beers typically brewed during the summer. Typically saison yeast is pitched at a temperature around 20C° and then raised a few degrees each day until you hit ~26° While 30° seems on the high end for saison its doable; fermenting higher will likely result in increased fruity or spicy character.
You don't necessarily need any complicated equipment to brew a normal ale. You could utilize any tub of water and ice packs to keep a fermenter cool. See this Question for more information.
saison/farm house ales. I was planning on for this summer as well :) They do well in the higher temperatures. http://en.wikipedia.org/wiki/Saison