You can collect seeds from just about any plant, just make sure they are dry before storing them, then they need to be stored in a paper bag preferably, kitchen roll would do at a push, kept dry and cool.
Antirrhinums (snapdragons) are perennials but usually treated as annuals. I leave mine in, cut off the flowered spikes and they sometimes live, sometimes not, but worth a try.
The book says you can sow these Spring or early autumn and over winter them.
When grown from seed and they have a few true leaves, nip out the centre and they will make into a nice bushy plants.
Can't think why they have gone out of favour a bit, such stunning plants and watching the bees on them is great fun!