Making seed balls or bombs is a great way to plant large areas with little input, and can be used with any kinds of seeds and for many purposes. The basic idea is to roll little 1" balls of clay, compost, and seed and throw them on where you want them to grow.
My favorite way to do it is to select a "guild" of companion plants that will help eachother grow, and initially mix these seeds together. For instance, lettuce, carrots, green onions, and radish's will all grow well together and prefer to grow in similiar conditions. Mix the seeds with clay and compost and roll into balls. Seed balls are thrown out into the desired area...perhaps an old flower bed...and a light mulching can be applied. Once the rain comes or the bed gets enough water the clay balls fall apart as seedlings emerge.
Another option for seed balls is forming soil building guilds of plants and fungus that will nuture your specific soil. Traditional cover crops such as clover and rye can be planted with seed balls, and peas and beans will help the soil and help feed people too. More specific plants can be used to mine nutrients from the sub soil...stinging nettle for instance helps to mine calcium and iron from the subsoil, making it more available for neighboring plants. Perennial rootsystems help to aerate soils and prevent compaction. Beneficial mycorrhizal fungus can be mixed into the seed balls to help plants roots form and they provide extra water and complex nutrients that plants cannot process alone. With a little research and a big enough bag of seed balls whole acres of plant communities can be established.
The Material Mix Options
1. Seeds, preferably beneficial guilds
2. Dry sifted clay
3. Compost (fresh goat, sheep, and rabbit manure works great if you don't mind handling it)
4. Beneficial mycorrhizal fungus (optional but super beneficial)
5. Lime or other mineral additives to balance soil PH ( beneficial but optional)
6. Water
The Process
1. Mix equal parts seeds, clay, compost and anything else you're using
2. Mix water in until the mix can be rolled into 1" balls
3. Allow to dry until hardened
4. Look like a maniac throwing manure balls all over the neighbor
5. Wait
6. Wait
7. Rain
8. Be amazed at the pure potential of seed
There are a few classifications of fungus...endophytic, sapropytic, and mycorrhizal. Mycorrhizals are found on nearly all plant roots, and some actually grow into the plants cells, feeding on excess sugars from the plant while bringing nutrient and water to the root hair. I used a seeding mix from Fungi Perfecti, www.fungi.com, and found that the difference in seed flats is amazing. Seedlings emerge in sometimes half the normal germination rate, have great growth, and seem to be immune to dampening off (tiny seedlings getting rotten stems). I highly reconmend including mushrooms and fungus into any plantings, and think they are especially good for techniques like seed bombs.