My problems have passed. I did a few things last night to troubleshoot things and think my issue was either with my provider or just some cache on the network. Here is what I did.
On my iPhone 4, I could not connect to the app store. So I powered off the phone, reboot, and tried again, no go. The app store worked fine earlier in the day at my office so I turned off my wifi on the phone and let it try via 3G. Success! After I logged into the App store I immediately switched back to wifi and it kept working for several more app udates. But that told me that it was either my own network or my ISP and it was just the initial connection that was broken. So I powered off all of my equipment at the house (router, AP, etc...) and when they came back up, all my devices can connect to the app store and my AppleTV is working again just fine.
In my case, I think Apple may have changed some IPs and my equipment still had some cached DNS records that only clear after some time passes or a reboot of the router. My router and network equipment is rock solid so it hasn't been rebooted in over a year. The issue would have passed eventually, but a reboot forced it to flush now and I'm golden at home again.
Apple may have had a glitch recently that caused all of our issues, but things seem to be stable now. I would suggest that everyone make sure their DNS cache is clear on all their devices.
For routers that usually just means rebooting them.
For computers you can run an "ipconfig /flushdns" (Windows) command or the Mac equivalent - or just reboot as well.
For devices (like iPhones/iPods) a reboot should be good.
You should start with routers/firewalls/Wireless APs and then move to your computers and devices. After everything is rebooted and/or flushed, try each device to see if your connection to iTunes is restored.