RANCID - Really Awesome New Cisco confIg Differ

RANCID -A great, simple ,light weight tool for system and network administrators.It's really awsome as it's name suggests.
Rancid is a combination of shell, Perl, and Expect scripts that work together to provide configuration management. Although the name implies Cisco-only support, the tool has grown to work with a multitude of devices from most major vendors. Adding extensions for new device classes is also fairly easy.
Rancid currently supports Cisco routers, Juniper routers, Catalyst switches, Foundry switches, Redback NASs, ADC EZT3 muxes, MRTd (and thus likely IRRd), Alteon switches, and HP Procurve switches and a host of others.