Here are some organizations who have developed and shared their social media policies and guidelines:
Municipality of Chatham-Kent: Social Media Best Practices
Town of Collingwood: Use of Social Media Policy
Town of East Gwillimbury: Social Media Strategy
City of Guelph: Questions to Ask When Considering New Web Tools
City of Guelph: Guidelines for Engaging in Social Media Conversations
City of Guelph: Social Media Guidelines for Employees
City of Guelph: Social Media Guidelines for Elected Officials
City of Guelph: Social Media Commenting Guidelines
Lambton County: Online Social Media Policy
City of London: Social Media Policy
City of Markham: Corporate Social Media Policy
Municipality of Strathroy-Caradoc: Website & Social Media Policy