There are a number of assessment tools and techniques used by EA practitioners that can be found on-line. A short list of examples is attached in the documents below.
Each is concerned with assessment of the Enterprise Architecture function itself - how well EA is accomplishing objectives within an organization as a whole or as measured in reference to a particular initiative.
In some cases, such as the State of Oregon Method Assessment, a tool is used to assess an EA function just starting out.
Other examples, such as the Enterprise Architecture Realization Scorecard, the tool is used to assess the impact of the EA function on a particular initiative, such as establishing a data warehouse.
Links to Assessment Examples:
State of Oregon Gartner Method Assessment
The Enterprise Architecture Realization Scorecard
University of Nottingham EA Self Assessment
GAO Executive Guide "A Framework for Assessing and Improving Enterprise Architecture Management"