I have saved pumpkin, tomato, capsicum and other plant seeds too
I saved them from last year and all have done well. With the pumpkin and tomato I placed them evenly apart in rows on a paper towel (quite hard with the tiny tomato seeds) and placed another paper towel ontop, let it dry then cut it so it could fit in an envelope and placed them in a cool dry dark place. When I planted them I just cut the paper towel into little suqares with a seed in the middle and poped then into seed rasing mix/compost, they all sprouted
I collected seeds from a supermarket brought capsicum and put them directly into an envelope to store then scattered them in a tray of compost/seed raising mix and they all sprouted (about 100 of them) costed me nothing
Going to do more this year and see what I get/works
My vege boxes randomly have sprouted tomato plants from last year... I have sooo many its crazy! and I noticed something growing between the broccoli so left it to see what it was and Im pretty sure its a sunflower.... dont know how it got there but its growing heaps by the day!