How long does it take to make a call to a data center from where I am? This is a very important question for all things related to computer communication.

There are 2 really cool website taking care of this question:

http://www.azurespeed.com/

https://azurespeedtest.azurewebsites.net/

AzureSpeed.com

Check out http://www.azurespeed.com/ :

Azurespeed.com will let you select Azure Regions and show you the latency for all the regions from your current IP location:

Additionally, you can test things like Upload, Download or CDN speed for your selected regions:

Azure Speed Test 2.0

https://azurespeedtest.azurewebsites.net/ does the same as AzureSpeed.com but the UI is a lot sexier. It will call the blob storage service in different regions and order them by latency. Great stuff.