Annabel - it pretty much depends on the size of the flower - big flowers, like the Cattleyas used for cut flowers, such as corsages, will produce big pods when pollinated. Smaller flowers produce smaller pods. Hope that helps!
Tucker

Cymbidium madidum produce large pods. Not long like Vanilla but wide/fat. The flower, on the other hand, is quite small.

Many orchids produce large seed pods relative to the size of the plant. These may contain hundreds of thousands of tiny dust-like seeds. The pod may last for many months before finally breaking open, when the seeds are scattered by the wind. The reason for this is not that orchid seed has low fertility but because of the very specialized growing conditions needed, ie. in cracks in the bark of trees. Terrestrial or ground-growing orchids are more like "normal" plants! - Ian.