apt hunting in Santiago

I am not aware of a craigslist type site here in Santiago. A possibility could be needish.com

A friend of mine comes frequently for a few months per year. She uses contactchile.cl The apartments are of a very high standard but you pay slightly more then renting from locals. I guess it depens on how long you want to stay. Finding an apartment from abroad is difficult and at least with contactchile.cl you will know it is a good standard.