Of course there are many types of cushions and mats, but I think the traditional ones (round zafu/kapok-stuffed) are the most versatile and best suited for long practice. I always direct my own students to purchase their sets from Chopa. They have a very nice zafu/zabuton set for a very reasonable price - go here to see it:
We require the set to be black in color (the traditional color), so you might want to check with your dojo before you show up with any other color - if that stuff matters where you train.
Hope that helps,