Jackson Core

org.codehaus.jackson	Main public API classes of the core streaming JSON processor: most importantly JsonFactory used for constructing Json parser (JsonParser) and generator (JsonParser) instances.
org.codehaus.jackson.annotate	Public core annotations, most of which are used to configure how Data Mapping/Binding works.
org.codehaus.jackson.impl	Parser and generator implementation classes that Jackson defines and uses.
org.codehaus.jackson.io	This package contains I/O helper classes Jackson itself uses, but that are not exposed for external reuse.
org.codehaus.jackson.sym	Internal implementation classes for efficient handling of of symbols in JSON (field names in Objects)
org.codehaus.jackson.type	Contains classes needed for type introspection, mostly used by data binding functionality.
org.codehaus.jackson.util	Utility classes used by Jackson Core functionality.

Jackson Mapper

org.codehaus.jackson.map	Contains basic mapper (conversion) functionality that allows for converting between regular streaming json content and Java objects (beans or Tree Model: support for both is via ObjectMapper class, as well as convenience methods included in JsonParser
org.codehaus.jackson.map.annotate	Annotations that directly depend on Mapper classes (not just Jackson core) and are used for configuring Data Mapping functionality.
org.codehaus.jackson.map.deser	Contains implementation classes of deserialization part of data binding.
org.codehaus.jackson.map.ext	Contains extended support for "external" packages: things that may or may not be present in runtime environment, but that are commonly enough used so that explicit support can be added.
org.codehaus.jackson.map.introspect	Functionality needed for Bean introspection, required for detecting accessors and mutators for Beans, as well as locating and handling method annotations.
org.codehaus.jackson.map.jsontype	Package that contains interfaces that define how to implement functionality for dynamically resolving type during deserialization.
org.codehaus.jackson.map.jsontype.impl	Package that contains standard implementations for TypeResolverBuilder and org.codehaus.jackson.map.jsontype.JsonTypeResolver it can construct.
org.codehaus.jackson.map.ser	Contains implementation classes of serialization part of data binding.
org.codehaus.jackson.map.type	Package that contains concrete implementations of JavaType, as well as the factory (TypeFactory) for constructing instances from various input data types (like Class, Type) and programmatically (for structured types, arrays, Lists and Maps).
org.codehaus.jackson.map.util	Utility classes for Mapper package.
org.codehaus.jackson.node	Contains concrete JsonNode implementations Jackson uses for the Tree model.
org.codehaus.jackson.schema	Classes needed for JSON schema support (currently just ability to generate schemas using serialization part of data mapping)

Jackson JAX-RS provider

org.codehaus.jackson.jaxrs

Jackson-based JAX-RS provider that can automatically serialize and deserialize resources for JSON content type (MediaType).

Jackson XML Compatibility

org.codehaus.jackson.xc

Package that contains Xml Compatibility functionality for Jackson.