Apache Camel is a powerful rule based routing and mediation engine which provides a POJO based implementation of the Enterprise Integration Patterns using an extremely powerful fluent API (or declarative Java Domain Specific Language) to configure routing and mediation rules. The Domain Specific Language means that Apache Camel can support type-safe smart completion of routing rules in your IDE using regular Java code without huge amounts of XML configuration files; though Xml Configuration inside Spring is also supported.
Apache ServiceMix is an Enterprise Service Bus (ESB) that combines the functionality of a Service Oriented Architecture (SOA) and an Event Driven Arthitecture (EDA) to create an agile, enterprise ESB.