Get some good ideas here!

• "Carbon Penance" a power monitor by Annina Rust that punishes the user
• Jason Winter's Real-Time power monitor
• Mazzini's project pushes data onto Pachube
• Pachube has lots of other projects!
• Furnace monitoring, using a DAQ board and phototransistor

Wanna just buy it?

• Black & Decker home electric meter watcher
• DIY KYOTO's power-clip Wattson is pretty
• CurrentCost

• Myenergyusage.org (one fellow upgrading his Wattson's software by hand)
• Wattzon.org (social energy information)