I bought a couple of seven inch screens, and they arrived yesterday. I'm using them to monitor my 100 mbit line traffic.
These cost about £18, and are intended for in-car use, for example, for reversing cameras. So they run off 12 volts, and use a composite video input.
PC power supplies give a 12 volt line, so that feeds the screen. The 12 volts also feeds one of those little £1 voltage step-down devices, which lowers it to 5.3 volts, and that goes to a Raspberry Pi. The version 1 Pi has a composite video output, isn't that handy? Later versions don't have that.
I do the display by using "montage" to create the graphic as a bmp file, then ffmpeg to convert it to an 800 by 480 framebuffer file. Then it's just a matter of copying that file to /dev/fb0. And it looks great. I have one in my office, and one in the data center.
I found a nice bargain on Ebay, and I got four 17 inch LCD monitors for £63. I'm not exactly sure what I'll be using them for, but I do use a lot of screens.
Another bargain I got recently is an Cisco ASA 5510 firewall. ASA is what Cisco did after the Pix. The command language is pretty much the same, but the 5510 has a much higher capacity than my current Pix 515E, which I'll use as an in-place backup, because if my firewall goes down, everything goes dark.