There has been a lot of talk, e.g. over at petapixel, about LightZone recently. It is a RAW converter and image processing tool written in Java, available for Linux and MacOS, that has been made open source just now.
At first glance it looks a bit like Darktable (due to the dark UI?) but I will check it out the coming weeks. G+ users here might be interested in the Open Source Photography Community over there.
The tool supports quite a number of cameras already (see here), but unfortunately there are still some cameras missing (like my 6D).
When the company that originally was making LightZone was shut down, fans of the software kept the project going and now the source was released to the community (BSD license). The original software was well received by photographers and it is going to be interesting to see what happens in the future…