Here are two KM maturity models that I have worked with.
APQC KM Maturity model: covers a comprehensive range of topics (objectives, business case, budget, resources, change management, communition, processes, tools, metrics). Learn more: http://www.apqc.org/km-capability-assessment-tool
Innovation Value Institute develops a number of IT-related capability models. They have one for Knowledge Asset Management (http://ivi.nuim.ie/it-cmf/knowledge-asset-management). This is tightly focused on repositories and distribution of the assets in the organization.
In practice I have used elements of multiple models to fit my organization's needs.