Good advice, GreenDragon.

I personally use Travelzoo to do my regular searches. All it does is crawl airline and booking sites (including all the legacy carriers, plus Kayak, Orbitz and whatnot) and star the ones with the best fares for your route, but over the past few months alone, I've found ORD-SJO r/t on AA for $400 there and ORD-PRG r/t on LH for $800 (both including taxes and fees). I've found some great deals there over the years.