Our newest idea was to tear up a tea towel, wet & freeze the pieces & drape them over the cage. Along with a fan directed at the cage, this seemed to help a lot. Of course, the traditional ice in their water bottle & ice cubes to munch on helped too!
We've also been keeping watermelon on our shopping list this summer, helps keep our little fluffers hydrated.
I also like to set up their little paint-tray pool on hot days. Throw in a few ice cubes & frozen peas. The little rattums enjoy it.
Beyond all my usual "it's hot as hell" options, I also have a great recipe to share, thanks to Robin's Hammocks:
P'Nut Butter Banana Ice Cream!
A nice cool, healthy treat in the summer for your ratties!
Freeze & enjoy!
32oz Plain yogurt (nonfat) 4 Ripe bananas 1 Cup peanut butter Blend together until all mixed & no chunks Pour into ice cube trays (takes about 6)
Hope some of my summer suggestions/ideas help. Comments with other suggestions are more then welcome :D