From the TechNet description:
Microsoft Dynamics Lifecycle Services provides a cloud-based collaborative workspace that customers and their partners can use to manage Microsoft Dynamics AX projects from pre-sales to implementation and operations. Based on the phase of your project and the industry vertical, the site provides checklists and tools that you can use to help you manage the project. It also provides a dashboard so that you have a single place to get up-to-date project information.
Lifecycle Services is available to customers and partners as part of their support plans. You can access it with your CustomerSource or PartnerSource credentials. Go to the site.