Entangle allows for tethered camera control and capturing from most Nikon and Canon DSLR cameras under Linux. The camera's shutter can be triggered from the open-source program on Linux, there's support for live previews, automatic downloading and display of photos, and controlling of all camera settings from the computer. Basically you can remotely control the camera's setting and proceed to take photos via the camera's USB connection. This software is licensed under the GNU GPLv3+ and is built atop libgphoto, so it's a bit catered towards GNOME.
Entangle 0.4.0 is the new release from 8 July and it features support for multiple windows and cameras, syncing capture/preview across windows, support for applying aspect ratio masks to images, key bindings for common actions, support to render a focus point during preview, support for grid lines on previews, and many other changes.
Those wishing to learn more about Entangle or to download its latest release, visit Entangle-Photo.org.