Phil, I just read the description on the pack of seeds and it normally says to what purpose the cultivar is most suited.

Here is an example from one of the seed companies I have used previously:

http://www.johnsons-seeds.com/seeds-plants-gardening/15093/coriander-cilantro-for-leaf
http://www.johnsons-seeds.com/seeds-plants-gardening/11754/coriander-for-seed

After a quick Google search I came across this cultivar list if you are interested:

www.myfolia.com/plants/563-coriander-coriandrum-sativum/varieties

Just to add to the advice already offered:

-Coriander doesn't appreciate being transplanted, so plant seed where they are going to grow.

- Some companies offer 2 types of seeds. One would be grown for Coriander seeds, and the other will resist the urge to bolt so that you may harvest the leaves for longer until it does go to seed. The latter is some times known as Cilantro when you buy the seeds, and yes, I do realise this is another name for Coriander. Both produce seeds and leaves, it just depends on which is more important to you to which strain you grow.