Tagging on Compute, Network and Storage Resources

Consistent use of tags on Compute, Network, and Storage resources created through the Azure Resource Manager allows organizations to track their usage in a new way. By analyzing your tagged Azure resources and usage data, powerful consumption insights can be gained – insights that can enable better cost management and allocation throughout your organization.
What are tags?
Tags are user-defined key/value pairs which can be placed directly on a resource or resource group. Azure currently supports up to 15 tags per resource and resource group. Users are able to sort and organize resources by tags. Also, once a tag is placed on a billable resource, created via the Azure Resource Manager, the tag will be included in the usage details found in the Usage and Billing portal. Please note that tags are supported for Compute, Network, and Storage resources created through the Azure Resource Manager only.
To learn more about Azure tags, check out Using Tags to organize your Azure Resources along with How to Tag a Virtual Machine in Azure.
IT Financial Management Partner Solutions
Azure has many partners that are already incorporating tags into their cost management solutions. To learn more about these solutions and how tags are being leveraged, please check out the links below:

Apptio
Cloudability
Cloudyn
Cloud Cruiser
Hanu Insight
RightScale

Getting Started

Azure Resource Manager Overview
How to Tag a Virtual Machine in Azure
Using Tags to organize your Azure Resources
Gain insights into your Microsoft Azure resource consumption
Understanding your Azure Bill

http://azure.microsoft.com/blog/2015/07/30/tagging-on-compute-network-and-storage-resources/