Some informative links:
Thyroid.about.com - great discussion board and tons of info
Gail's Thyroid Tips
www.thyroidhistory.net - extracts from past and mostly forgotten papers, quite the research resource!
Basal temps are a great way to track thyroid function. Take them: first thing in the morning, before getting out of bed, about the same time each morning (not the morning you sleep in two hours), days 2-4 of cycle if menstr. Give the thermometer 4 minutes for digital or 10 for glass. Write it all down on a calendar along with your med doses, symptoms, etc, and you should be able to see patterns. The goal is 97.8-98.2 F armpit. Some people find that their oral varies very little (0.1) from their armpit. I'm not sure why. (I'm one of those people and have talked with several others.) Hence I have no opinion on the doctors who suggest doing oral 3 times/day. Whatever works. Also, I have found some variation in thermometers and am about to go out and buy a new one because I am so displeased with the 2, yes 2, that I have. They differ often by 0.4 or more and have wide error ranges, so obviously this is not acceptable. I plan to buy a Basal Temp thermomter, which they sell in the "family planning" section of the pharmacy.
It should be said that thyroid function is not the only thing that affects basal temps, as they can also reflect adrenal function for instance. Since the thyroid and adrenals balance each other, it makes sense that you have to balance both things to get them optimal.