Here are some vendors of plantable "seed paper" that we can use for promotional items:

http://www.mainstreetseedandsupply.com/promopackets.htm
http://www.humeseeds.com/promopkt.htm
http://www.westsky.com/seeds.htm
http://www.farfromboring.com/Promotional-Products/Eco-Friendly/Plants-and-Flowers/sc-609.html
http://www.greenfieldpaper.com/asccustompages/products.asp?categoryID=13
http://www.seedcards.com/
http://plantableseedpaper.com/