We always get too many of some seeds at the Seed Swap, do bring a few, but here are some ideas of how to use the rest:
Calendular, or pot marigold: These seed so abundantly and are so easy to harvest you can sprinkle them around and use as a green manure in autumn or spring. The green leaves will enrich the soil or your compost heap and you can leave or transplant a few to flower.
Fennel, the seeds make a great tea, good for the digestion.
Nigela (love in the mist), The seeds are edible and good in rice puddings etc.
Poppy seeds are also edible, and often used on bread.