Mule is the leading open source ESB and integration platform, with hundreds of mission-critical production installations worldwide.
Mule is the most widely-used open source integration platform for moving and managing data between disparate enterprise systems. As the messaging backbone of choice for many of the world's most high-performance, multi-protocol environments, Mule securely and reliably moves mission critical enterprise data.
Whether for SOA, EAI, connecting internal systems with Salesforce.com or moving and transforming JMS messages around your infrastructure, Mule has multi-purpose functionality to support the wide range of integration challenges a typical enterprise faces. Mule can be used for system-to-system messaging, as transactional middleware or as part of an application server. 
Adaptive Integration
Mule allows developers and architects to seamlessly stitch together services and application networks without affecting their existing IT infrastructure. This adaptive approach frees developers from the rigid use of proprietary standards, toolsets and deployment patterns. Mule adapts to an enterprise integration requirement rather than defining it.
With support for a broad base of standards, protocols and technologies the extensible nature of the Mule core server offers enterprises maximum flexibility of choice for how they build their integration solutions
Simplicity in development
Mule's simplified programming model creates the same results as expensive proprietary applications, at a fraction of the cost both in terms of software licenses and professional services. New users are up-and-performing integration tasks in 5 minutes, literally. The open source code base allows Mule users to customize the product to meet their needs.
This rapid development and deployment cycle means that developers can go from laptop to fully-networked environment in just minutes through simple configuration and controls.
Open Source Advantage
Mule is leading the next phase in the evolution of enterprise middleware - where the advantages of open source development and distribution methodologies have created an integration alternative that delivers features and functionality beyond what's available from proprietary vendors.
The open source approach to integration isn't just about lower cost. Mule's thriving developer community (more than 58% create extensions and plugins) gives enterprises access to a rate of innovation that can't occur with proprietary integration products. Mule's complete code transparency allows developers to customize Mule to meet their unique IT environment needs, while taking advantage of the new connectors and enhancements continuously being created by the Mule community.