I have to turn off and on my WiFi every hour or so. What's wrong? In my home network, my Apple TV, iPad, and Macbook Air all have the same problem. The WiFi network works fine, but after about an hour or less, the Wifi stops working. Things just hang when I try to things like open a webpage or ping yahoo.com. The WiFi signal icon is still on, however. The fix for me is to turn off my wireless on my Apple device and turn it back on again. 

But this is annoying. How can I fix this? I'm using a Zonet Wifi router with WPA2 on. My ASUS Ubuntu netbook has no problems staying on the WiFi network.
I agree that since your problem occurs over many devices it is unlikely to be a problem with the Apple devices. I appreciate your point about the Ubuntu device still appearing to work, but it still seems more likely to be a router problem (it could be for example the router is producing multiple errors that the Apple software is catching).

I'd suggest a hard reset of the router as Step 1 (before you do so however make sure you know ALL your current router settings, not just your name and password. I take a screenshot of each setting page)

Most routers have a Reset button you have to press with a paperclip.

Power off the router for several minutes, then apply power and do an immediate reset.