Summer heat is bad for desktops and especially laptops. Here are a couple of things to do to protect your computers.
For desktop / tower computers vacuum the outside vents in the front and the back. If you are feeling adventurous with the computer unplugged open the side panel and vacuum the dust on the bottom of the computer. Be careful to stay away from any wiring and electronics. Raising the tower from the floor by even 2 inches using a few books will reduce the amount of dust the computer sucks in.
For laptops use a laptop cooler they come in two styles usb and outlet powered. I prefer the outlet powered kind so the usb does not get strained and you don’t loose a port.
I thought this one is interesting but I haven’t tested it myself. It comes with a usb hub in the back so you can have all your devices connected. This way when you come back to your desk you only have to connect one cable to your laptop.
http://www.newegg.com/Product/Product.aspx?Item=N82E16834999415&ignorebbr=1
Here is a link for all types sorted by reviews.
If you use your laptop on the bed or couch use a simple tray. This will help prevent heat and lint getting into the laptop.