The latest rollup update 5 is available for download at

http://www.microsoft.com/download/en/details.aspx?displaylang=en&id=27820

This rollup is necessary if you want to use the Activity Feeds solution available in the marketplace.

One of the new features added on this rollup update is the ability to add hyperlinks of the records you want to access dynamically on email notifications via workflows.

For more detail information check this link:

http://www.powerobjects.com/blog/2011/11/11/microsoft-dynamics-crm-2011-update-rollup-5-adding-a-hyperlink-to-email-notifications-via-a-workflow/