The many Libraries for Processing will generally just work on the Raspberry Pi. Below is a list of a few that Raspberry Pi users might find useful:
- GL Video - for hardware-accelerated video playback
- Simple Touch - for using touchscreen displays
- Simple Receipt Printer - for using Serial-port-attached thermal printers
- Upload to Pi - a tool for uploading sketches onto Pi computers remotely from another machine
- Hardware I/O - will run in emulation mode on other OS
All of these are available to install through Processing’s Contribution Manager.