In the Garden
There are many benefits to saving your own seed. Of course, there is the obvious benefit of saving money! The seeds you save will be better adapted to grow in your region/environment. Growing heritage seeds allows for more diversity in our food supply.
Here is a nice blog article: 40 Reasons to Save Seeds.
Do your research. Some seeds require certain protocols for saving i.e. fermenting tomato seeds. Also, you cannot keep seeds of hybrid plants because they were made by crossing two plants and so the seed will not be true to the parent.
I didn't get around to saving as many seeds as I had hoped but it was also my first big year of gardening so I had lots of things to monitor.
Here is a list of things I did keep:
a flowering tobacco plant that I just LOVE the color of
dill (I also shook the plant really good to try and get it to self seed)
broccoli (although I did buy a new broccoli so I am not sure I will actually grow these)
a green frilly lettuce (I need to do a better job of labeling things too)
Our library in Moscow started a seed library last year. I finally got around to checking it out this winter.
The idea is that you can take some seeds and leave some seeds. I took some lemon balm and Cinderella pumpkin seeds. I left some arugula and calendula seed. They have very nice directions on how the library works.
I have already placed one seed order and it was about $50. I still have more seeds to order! It is just way too much fun to sit and look at the seed catalogs and dream about the garden...