Service Oriented Architecture (SOA) is an approach for building distributed systems that deliver application functionality as a set of self-contained business-aligned services. It promises lower integration costs, increased reusability and improved enterprise agility and adaptability. One of the key obstacles for SOA is the presence of existing legacy applications that support critical business processes but are inflexible and hard to adapt for integration with other business applications. This paper presents a survey of key approaches to integrate/transform legacy applications into services to participate in an enterprise-wide SOA. It also presents a decision framework to guide architects in selecting the optimal combination of legacy modernization options.