I found this nice two color 128x64 pixel OLED display on eBay and thought it would make a perfect display for a simple temperature and humidity meter.
I've added a BIG 32 pixel monospace font for the thermometer (only numbers and few other characters are implemented). Note that only the top part of the display is yellow and the bottom part is always blue, so you can't change color of any pixel.
Total cost of hardware for Arduino Nano, DHT temperature and humidity sensor and blue/yellow 128x64 OLED display is not much more than 10 dollars on eBay.
Step 1: Connect the OLED Display and DHT21 Sensor to Arduino
Connect the OLED module to Arduino
OLED Arduino ---------------- SDA D9 SCL D10 RST D13 DC D11 VCC 5V GND GND
Connect the DHT21 (AM2301) temperature and humidity sensor wires to Arduino
DHT21 Arduino ---------------- yellow D5 red 5V black GND