We're getting quotes to get the house insulated, as we figured collectively we're spending upwards of $10,000 a year heating the place (yikes!).
One of the insulators (ZeroDraft - Kennebunk, ME) recommended using polyurethane spray foam down in the basement and crawlspace to fill in the cracks. Here's what it looks like - you can see how it gets in the nooks and crannies. On new construction, they spray it in the walls before the sheet rock goes up. You can't do that in old houses, you need injectable foam or something which no one we talked to does.
This particular insulation guy only recommended working on the basement and attic, and not bothering to insulate the walls. We all think this is dumb. Plus, his quote was way high, so I think he just didn't want the business.