When your kitchen pot isn't big enough, cut the top off a beer keg and put it on your outdoor propane burner! Notice the valve on the bottom. That's good for cooling the tomatoes fast. Drain out the boiling and refill with cold. 15 gallon capacity baby! Now that's how to fill a freezer for the winter.
I have about 6 gallons worth of ripe tomatoes so I put an equal amount of water into the pot. Remember that the tomatoes will displace the water and the more water you use the longer you have to wait for it to boil. A 1:1 ratio of tomatoes and water is what I go by, making sure that the two don't add up to more than the pot's capacity.
Once the water is up to a light boil the heat can be turned off. They only need to blanch for a few minutes, and the riper they are the less time they need. I throw them in by hand rather than dumping, the least ripe ones in first and as soon as I finish throwing the ripest ones in I drain the hot water and immediately fill with cold water to stop them from cooking.
The next thing I like to do is quarter them and cut out the stem and white part. Then I throw them into a strainer to let some of the juice drain out. Under running water, I rinse out the seed and remove the skins and any bad parts and return them to a pot (or two or three) and at this point my five gallons of tomatoes is down to about 3 gallons.
Now to chop them. If I only have a few, then I just chop by hand, but for this many I get out the food processor to make quick work of it. Finally, using a ladle, I scoop the diced tomatoes into quart or gallon bags for the freezer.