There are many good ones and not too many bad ones.
Some people have success using plain sand or gravel. The majority use a base layer nutrient and then 'cap' it with sand or gravel.
Good ones off the top of my head:
ADA Aquasoil (No fish for at least a month) Needs no capping
Tropica
Eco-Complete
Onyx Sand (especially good in non CO2 tanks)
Many others available. Take a look on AquaEssentials.co.uk
Andy