Requirements

Before I get too far down the road, I need to establish some high level specs.
The end product will:

• measure incoming water temperature (EWT)
• measure outgoing water temperature (OWT)
• measure return air temperature
• measure supply air temperature
• measure supply humidity
• measure outside temperature
• log the data somewhere somehow
• display the data on an LCD (of course)

It will be nice to have:

• measure KWh usage for whole house 
• measure KWh usage for HVAC
• pulse monitor for water meter (have one sitting in the closet)
• keep track of seconds the burner in the water heater is running
• RTC for data tagging

Devices:

• DS18S20 temperature sensor (few in the drawer)
• PIC16C84 (if we cannot smash the code in there, we will buy a bigger one)
• HSU-07 humidity sensor
• 16x20 LCD (need a good cheap source)
• Bluetooth serial module (these ain't the dark times with cables and stuff)
• 433MHz wireless modules (just in case)
• 74HC138 will slim down the 1-wire
• Flame sensor - Cool!

Misc:

• Google for data logging
• DesignSpark for PCB creation (seriously, I tried Eagle and could not figure it out).