Raspberry Pi

Pibrella an easy way to play with electronics on your Raspberry Pi.

GitHub - raspberrypi/firmware/boot Boot Firmware files.
NetBSD/evbarm on Raspberry Pi
Raspberry Pi Thin Client project

The Bendyworks Blog - Getting Plan 9 running on the Raspberry Pi
itToby - Using a Raspberry Pi as a Thin Client for RDP/RemoteFX/VMWare View or Citrix

WiringPi is a GPIO access library written in C for the BCM2835 used in the Raspberry Pi. It’s released under the GNU LGPLv3 license and is usable from C and C++ and many other languages with suitable wrappers.
Pi4J a friendly object-oriented I/O API and implementation libraries for Java Programmers to access the full I/O capabilities of the Raspberry Pi platform.

moOde audio player
Runeaudio 2022-06-05: Seems to be dead. Try GitHub - rern/rAudio-1
Max2Play
piCorePlayer
Volumio

reddit - Volumio alternatives?

Tested to work with RuneAudio_rpi2_rp3_0.4-beta_20160321_2GB.img.

1. Attach the HiFiBerry DAC RCA+ Pro to the Raspberry Pi 3.
2. dd RuneAudio_rpi2_rp3_0.4-beta_20160321_2GB.img to the SD card.
3. Insert the SD card into the Raspberry Pi 3.
4. Boot the Raspberry Pi 3.
5. SSH into the Raspberry Pi 3. Default username/password: root/rune
6. Open /boot/config.txt in vi and remove the # from the line:

   #dtoverlay=hifiberry-dacplus

7. Reboot the Raspberry Pi 3 via the Runeaudio web interface or with 'reboot' on the SSH prompt.
8. Open the Runeaudio web interface.
9. Go to Menu → MPD.
10. In the pull-down menu at Audio output interface “HiFiBerryDAC+ (I2S)” should now be selectable, select it.
11. Set Volume control to “enabled - hardware”.
12. Click on “Save and Apply”.
13. It should now be possible to play audio via the HiFiBerry DAC RCA+ Pro.