Hot water is a pretty significant cost for home utilities. A little while ago I bought a small attachment for my shower at home that automatically cuts down the water flow to a trickle once the water has heated to 95F.
The Energy saving 'Ladybug shower adaptor' that I bought cost $30. They also have a combined Low flow shower head plus energy saving showerstart for $40. The products literature cites a $0.03 cost per gallon for hot water. I found a similar figure with the Shower Savings Calculator.
I normally run my shower in the morning waiting for the water to heat up. The shower is on the opposite end of the house from the hot water tank so it takes a while for the water to travel the pipes and get the hot water at the shower head. While I'm running the water I tend to take care of other morning activities such as brushing my teeth, etc. So I'm usually wasting a little bit of water since I'm not standing at the shower waiting to start showering the instant that the water is sufficiently heated up.
Now however with the attachment installed it will shut down the water flow when the shower is heated up. This saves by not sending wasted hot water down the shower drain. If I save just 1 gallon a day its $10.95 per year and 2 gallons a day is $21.90. With two people using the shower right now I'm easily saving $20 a year with this attachment. Plus theres added convenience of saving a little time by knowing exactly when the shower water is hot and ready to go. Plus I'm saving water.