Determining Appropriate KPIs
The book, Understanding User - Web Interactions Via Web Analytics, provides some suggestions on determining KPIs.
An article that I really like is Ten Characteristics of a Good KPI by Wayne Eckerson. The article presents KPIs as communications vehicles, which is a really interesting take. As communication vehicles, KPIs enable C-level and other executives, leaders, and managers to communicate the organization's mission and focus to stakeholders.