Mammoth PostgreSQL Replicator uses a transaction log and async replication model that nearly eliminates extra load on your master server regardless of the number of slaves you have in production. It supports advanced features such as large object, role, and ACL (grant/revoke) replication. It also supports promotion and failover.
MySQL Split Read/Write for Drupal is a patch for Drupal versions 5 and 6 that allows a Drupal-based Web site to access a multi-server MySQL setup with master/slave replication. This allows Drupal to send all MySQL select (read) queries to the slave nodes, while allowing insert, update, and select (write and read) queries to be pointed at the master node. The code modification allows for an increased 30% improvement under query-based transactions on this platform environment.
Cressida SynQuest for WebSphere MQ is a highly optimized, production-strength replication and synchronization tool utilizing the MQI API exit facility. It is designed to keep the content of WMQ queues on separate queue managers synchronized by performing a MirrorQ type application. SynQuest provides a solution for maintaining disaster recovery backups of queue managers in those cases where a hardware solution (i.e. mirrored disks) is impractical due to distance or associated hardware costs.
Galera wsrep provider is a dlopenable generic replication library which implements the wsrep provider API. It provides very efficient synchronous replication, and multi-master and "parallel applying" capabilities for opaque data buffers. Its primary focus is data consistency. A transaction is either applied on every node, or not at all. It works anywhere TCP works, including on WAN, and can utilize UDP multicast where available. It is used by the MySQL-wsrep patch project to create true multi-master MySQL/InnoDB clusters.
zrep provides an easy-to-use program to manage zfs filesystem replication and failover. No configuration files are required. The program is developed under Solaris, but may work with any up to date zfs implementation. The executable is a single script. Initialization does a full data copy, but subsequent syncs are incrementals. It uses internal locking to make sure there is no danger of overlap if you just shove it in cron to run every minute. Design target is more "near-time replication", since the sync can be run every minute or more. However, it could conceivably be used for "backup" purposes as well.