The Open Source Hardware Association (OSHWA) runs a free program that allows creators to certify that their hardware complies with the community definition of open source hardware. Whenever you see the certification logo, you know that the certified hardware meets this standard.
The certification site includes a full list of all of the certified open source hardware. Here is all of the hardware that was certified in July:
A USB seven segment display module created in Sri Lanka
The Olimexino-STM32, an ARM microcontroller-based arduino-compatible board.
4 flavors of Olimex Duinomites, which are industrial grade -45+85C computers running BASIC language interpreter with VGA display and PS2 keyboard.
14 flavors of the Olimex OLinuXino, a small linux computer with many options depending on the version you choose.
The Nautilus 3D printer from Hydra Research.
The BigFDM, a 3D printer with a 900x800x800mm build area.
The ANAVI Miracle Controller, a development board for controlling two 12V or 5V addressable LED strips via ESP8266 that features a dedicated slot for an I2C OLED display and slots for up to 3 plug and play I2C sensors.
4 flavors of the LCD-Olimex OlinuXino, TFT Color LCDs with LVDS interface for the Olimex OlinuXino.
The Olimex ESP32-POE-ISO, a galvano-isolated Power Over Ethernet board for ESP32 with Ethernet, WiFi, BLE and GPIOs, programmable with either the Arduino IDE or Expressif SDK.
A Parametric Optical Filter Stage from the Universidad Rey Juan Carlos in Spain.
The Olimex USB-SATA, which adds SATA drive to computers with USB host.
The Creatable D3 delta-style 3D printer.
Want to certify your hardware as open source? Start with this application form.