MidiSeq is a polyphonic MIDI step sequencer with some great features, such as note step advance, step modifiers (tie, half, strum, and accent), super stable internal clock, nice swing and two modulation sources with velocity, after touch and CC destinations. More details here.
MidiArp is an advanced MIDI arpeggiator with a few twists, check the details here.
MidiGAL is a simple Atmega328p based MIDI controller board featuring 8×2 LCD, MIDI IN/OUT connectors with LEDs, one encoder and one switch. It can run a bunch of different firmware variants (updatable via Sysex), including original unmodified MIDIpal firmware.
One cool firmware available for MidiGAL is MidiClk — high precision Midi Clock Tester/Generator that is capable of straightening up your DAW or iOS MIDI Clock. See more details here.
Midi2CV Mk2 is a DIY embeddable MIDI to CV/Gate converter with reasonable defaults and extensive configuration options, see more details here.