The libQtSerialization library is a Qt extension that makes it easy to serialize your data in a forward and backward compatible way. The library is composed of QWriter and QReader. The writer is straightforward - all you have to do is call a writeTag() function and the data is serialized. The reader is a little more complex as it supports special cases, such as sub-classes (so you can save a tree of classes) and arrays of classes (your tree may be composed of multiple instances of a given object).
Collage is a cross-platform C++ library for building heterogenous, distributed applications. Among other things, it is the cluster backend for the Equalizer parallel rendering framework. It provides an abstraction of different network connections, peer-to-peer messaging, node discovery, synchronization, and high-performance, object-oriented, versioned data distribution. It is designed for low-overhead multi-threaded execution, which allows applications to easily exploit multi-core architectures.