One house rule we use that dramatically speeds up the game is open-hand resources. No more asking "Does anybody have...?" incessantly. Just look around and get ready for your trade. The bulk of game time is actually just trading.
We also remove the bandit and rolling an 7 is an automatic free resource for the roller and a re-roll. This helps unblock a lot of players in the beginning who are just sitting around waiting forever for a brick or similar.
With these changes games are easily 2x or 3x faster.