Some seeds are super easy to save, and they don't readily hybridize. You need to start with open pollinated seed. I have an absolute favorite pole bean called Fortex. It's very hard to get the seed from seed companies, so I've been saving my seed for over 10 years. Squash and cucumbers are real easy to work with. Then if you're not terribly concerned, just save the seed from your best fruit/plants. If you're a purist, all you have to do is wait for a female flower to open, pollinate it with a male flower of the same species, then cover it with a bag to keep the bees from visiting it. Label that resulting fruit, and it'll be pure. Tomatoes are very easy. They generally self pollinate. Lettuce is super easy. Let your first planting go to seed, then harvest the seeds, or just pull the plant up and lay it where you want the next crop. I save flower seeds, and am not too proud to scavange them from public plantings. With all of the GMO stuff going on, I think it's a good idea to be able to at least provide some of my own seed, as well as having some to share with neighbors. I saved seed from a neighbor's squash last year. I bought the biggest butter cup squash he had, and saved all the seed. This year, I grew 185# of squash from a single hill. Ironically, the squash he had out for sale this year was tiny compared to mine!
I'll pass on the rhubarb lady! Don't need a potty mouth cluttering up my brain! I had a hawk try to take one of my chickens today. It had actually landed on the ground behind my coop! One of the girls didn't stop growling for a half hour!
Congrats on the composter. I have one, have a love/hate relationship with it, but if I found an other one for $25, I'd buy it. Broadfork is on my wish list, I've actually been toying with the idea of what it would take to make one.