Raspberry Pi print & scan server
I was pleasantly surprised at how easy it was (with a bit of Googling) to set up the Raspberry Pi 2 I'd had gathering dust on my desk as a print server. My increasingly venerable USB-only Canon MP480 works just fine under Debian, but having to boot my desktop to use it was becoming tedious - much of what I get done these days is laptop-based or even done on my phone.
Having set it all up, I can scan and print from any Linux box on the network (theoretically from Windows too, only I have none of those left), and, with the addition of the CUPS Print app, I can print PDFs and the like directly from my Android phone.
Update - putting some IPv6-only DNS on the Pi and pointing a Windows 10 VM at it via IPP, printing Just Works. Even more impressively, Windows drivers for your printer do not need to exist, as long as they exist for CUPS on the Pi. I just chose the generic HP PostScript printer suggested in the article and it works perfectly, which is handy as Canon have no intention of providing Win10 drivers.