So far, I have already saved seeds from:
Radish
Spinach
Red and green lettuce
Carrots
Cabbage
peas, both bush and pole
onions
celery
scads of seed potatoes
I had this year, for the first time, bunches of tomato plants starting from leftovers last year
I gathered a bunch of seeds from black raspberry plants yesterday, But I have never had much luck getting them to germinate. I know they need a cold phase, and kinda think they need to be soaked in acid a bit. (the acid in animals stomachs sometimes triggers the seeds to germinate)
I am still waiting for my squash and cucumbers. Things did not do well here this year because the ground never really warmed up sufficiently.