We are a web-shop, and the CMS we use is called Seagull (google Seagull Project) - it's relatively unknown, however has been in development for a few years now. It's quite powerful and robust providing many commonly used modules that are found in most sites (user, CMS, media etc.)
It's open source and the developers are quite helpful on the mailing list. Documentation is fairly decent with many howto guides for newcomers. Being a web-developer for over 7 years I highly recommend it.