There are some cracks and a 6" hole in the one pillar that is crumbling out pieces of what looks like plaster. The house is very old and there is plaster on most of the walls, but I always thought the pillars outside were brick, since they have lines that appear to be brick. With the way it crumbles out could it be a wood frame for support and plaster made to look like brick? How would I determine this and then how can I fix it? Thanks for any help.

Plaster is only for indoors. Water would have washed plaster right off the supports. It could be a Stucco finish, or else the bricks are just crumbling from weight. You may have to replace the posts.

http://www.lowes.com/lowes/lkn?action=productList&N=0&Ntk=i_products&Ntt=porch%20columns

Get a professional to look at them. You can get a free estimate, and ask the contractor how he plans to fix it.