I finally ran out of projects that could be done with the parts I had on hand so I placed an ordern with Digi-Key and another with Mouser. The Digi-Key order has arrived and contains a 4x3 keypad, some rotary encoder, thermistors with available data sheets and the matching resistors, some transistors, and a pair of relays. Once the Mouser order comes in, I should be able to do all but the most costly projects. I think I'm up to about $100 in parts. The last two orders were about $30 each with the most expensive part being the keypad at about $14. I also purchased a soldering iron last weekend that is included in the total.
Since I bought a new thermistor and resistor pair, I decided to quickly redo the USB Temperature Logger project to see how far off I was before. This time, I decided to plug the components directly into the Arduino as seen on the left. The temperature in my living room was 71.5 F based on the digital clocked sitting near the radiator. My desk, where the Arduino is located is a similar distance from the radiator as the digital clock. As you can see below, the values are similar to last time. I guess the thermistor values I used last time were accurate enough.