[joshvm]

My favourite el cheapo displays are the SSD1306 OLEDs. They're tiny and work over I2C (or SPI). Cost about $3 from eBay from China. It's a fun weekend job writing your own printf and plotting libraries, trying to figure out the various modes. I2C isn't enough to do real-time refreshing of the entire display, but it's perfectly reasonable to plot sensor readings when you're just updating a few regions. You can also get libraries for the Raspberry Pi and Arduino (via Adafruit).

I remember years ago being quite proud of implementing a software variable-width font (since this wasn't a character display). Quite slow on an AVR, but looked nice.