This is an interactive gallery of split keyboards, based on an earlier list by diimdeep.
The keyboards included are mechanical and have either two halves ar a "wedge" in the middle to allow the wrists to lie in a more natural position. Many are available for purchase, either assembled or in kit form. Some only have the source (plans) available, which means making (or ordering from a service) the circuit board and case from a manufacturer yourself.
A good resource for mass produced, membrane (non-mechanical) keyboards is Xah-Lee's Ergonomic Keyboard Reviews.
The mechanical keyboards shown on this site are further classified as follows:
Traditional : traditional ergonomic keyboard; the normal layout with a wedge in the middle.
Ortholinear : keys placed in a grid or near-grid.
Ergonomic : keys usually staggered by column rather than row, and almost always including thumb keys.
Dished : a shaped keyboard with thumbkeys and dishes or wells for the fingers.
The minimum and maximum number of keys supported by the keyboard. Some keyboards can be assembled with a different number of keys (for example, using a double-height key instead of two single-height keys). Other keyboards are available with several variations on the design. In either case, the filter is based on the maximum.
Two halves : two independent parts to the keyboard
Rotary encoder : one or more knobs which can press keys, useful for volume up/down, page-up/page-down, etc.
Trackball/point/trackpad : an integrated trackball, laptop-syle trackpoint, or trackpad mouse.
Display : a display on the keyboard, which can show status (Caps Lock, current layer, macros etc)
Wireless : no wires!
Mass produced : Reliably in-stock for immediate delivery. : Probably includes a GUI or other professional tool for configuring keyboard layout, macros etc.
Assembled : Available for purchase pre-assembled and programmed. : To distinguish this from the following categories, it omits keyboards where individuals are willing to assemble a kit for others — otherwise there's little point to the filter. A company should be willing to buy an "assembled" keyboard for an employee, but less likely to ask someone on Reddit to solder a kit (below) for them.
Kit : Kit (circuit boards, cases, components etc) available to purchase. : Some people will assemble a kit for you, for a fee.
Plans (source) : Open source keyboards, where files defining the PCB and case are available. Sometimes, a group of people will order circuit boards and/or cases together to save costs, this is a group buy.
Unavailable : The keyboard is no longer available, and was not open source