Each year I keep experimenting with freezing tomatoes, trying to find the best balance between effort and usability of the final product. Canning, of course, produces a result that is very high quality with very easy usability - but it's quite a lot of work up front. Freezing is quicker up front no matter how you do it, and it's also easier to do in small quantities - for example if you have just a couple pounds of tomatoes that will go bad if you don't do something with them.
So here's another method: This will work best for paste tomatoes (juicier ones will be too watery on thawing). Core and seed the tomatoes, then chop or dice. If you want a very finely chopped product, you could even do this with a few pulses in a food processor. Then package the tomatoes in quantities of 1-2 cups in quart freezer bags. Squeeze out the air, then spread the tomatoes out flat in a thin layer. Stack the bags in the freezer. Then, when you want to toss some chopped tomatoes into something you're cooking, you can thaw a bagful in a bowl of warm water in 10 minutes or so.