Let's look at the different steps, and see where the times goes, and how to make it shorter. I've found that overlapping steps when possible is the best way to save time.
Setup
If all your equipment is ready to go, this takes 10 minutes. I have a box of all my gadgets. So I have to grab the kettles, burner, etc., and I'm good to go. Keeping equipment in easy reach keeps this step quick.
Bringing mash water to boil
This is where the big burner comes in handy for sure. I can boil 7-8 gallons of water in a few minutes (10-15) on my propane burner. If you only have a stove, splitting the water into smaller kettles and using more than one burner will make this faster.
Cooling to desired temp
I just wait. This is probably a step I could make faster by using my chiller.. But I just wait.
Mashing
I don't think there's any way to make this step faster.
Bringing sparge water to boil
As long as you do this while you're mashing, it doesn't increase the length of your day at all. I like to get the water boiling, and let it cool, just in time for when I need to sparge. Timing is important there. Sometimes I'll put the pot on the stove on low, to maintain the temperature.
Cooling to desired temp
See above.
Sparging
I honestly don't think I've been sparging correctly, but see this post for more info on various methods of sparging.
Boiling off excess liquid (if necessary)
If this is necessary, go ahead and start your boil while you're sparging. This saves a lot of time. Also, a harder boil evaporates water faster, so turn up that burner. Just make sure you don't burn the bottom.
The boil
Can't really speed this step up. Good time to do other things though. Like clean.
Cooling
A wort chiller is necessary. Letting 5 gallons of boiling wort cool on its own takes all night. Get an immersion chiller or a counter-flow plate chiller. An ice bath works, but the chillers with shave minutes to hours off your day.
Transfer to fermenter
Practice makes perfect.
Cleanup
Try to cleanup as you go. If you can clean everything while the wort chills, you'll have 20 minutes left afterward to finish up.