Here's the easy way to produce masses of clean seed with little effort:

snip

So that means that if you are eating a very tasty tomato you can save
some of the seed and hope for the best, could be a fun thingy to do next
year.
This year I bought some seeds that were supposed to be tumblers and
planted them up into hanging baskets like I have done for years. They
grew and grew and it was soon obvious that they were not tumblers just
ord. toms of whatever variety I know not. They are however fruiting well
inspite of having very little to grow in :-)
kate