For FPGA development, Digilent's PMOD standard established itself successfully for easy connection of peripheral modules. It is based on a simple pin assignment schema, ranging from single-row 6-pin connectors to double and quad row setups.

In order to follow FPGA course materials, the following PMOD modules got developed:

8LED2 PMOD The 8LED2 PMOD is a quad-row module that provides a set of eight dual-color LED (red/green) that can be used to display FPGA output signals. The module is using THT design, which allows for simple DYI assembly.
16LED PMOD The 16LED PMOD is a quad-row module that provides a set of sixteen yellow LED outputs. This module is helpful to visualize 16-bit counters, or similar. The module is using 0805-size SMD components, requiring basic SMD assembly skills.
7SEG4 PMOD The 7SEG4 PMOD is a quad-row module that provides four multiplexed seven-segment LED digits. A single 4-digit 7-segment module from OptoSupply, type OSL40361 has been used.
7SEG9 PMOD The 7SEG9 PMOD is a single-row module that provides nine seven-segment LED digits. The LED segments are driven by the TM1640 LED controller IC, using a serial protocol.
TSLIDE4 PMOD The TSLIDE4 PMOD is a double-row module that provides four push-button and four slide switch data inputs. I needed this module for the IceBreaker v1.0 board, which provides only 3 push-buttons and no slide switches.
PMOD2NANO The PMOD2NANO is a quad-row PMOD adapter for the 40-pin expansion headers available on Intels DE0-Nano-SoC boards. It provides two double-row PMOD connectors for the DE0-Nano SoC.