My girlfriend's house was built in the 40's, and though it didn't have knob and tube, it was wired with 2 conductor, so no receptacles were grounded. My dad (journeyman electrician) called it "BX Cable", and it basically looked like very old 1/2" flexible conduit. He and I had the pleasure of re-wiring it from underneath, via her unfinished basement, along with adding a few receptables, basement light fixtures, fixing the doorbell circuit, etc. etc. etc. The panel was fortunately upgraded in the last decade, though our new work required several doublers.
So yea, houses, good times. I hope to buy my own next year