Jerga, argot, or Spanish slang, may change year by year, but there are a few core phrases that always hit the mark. I was surprised by the BBC Cool Spanish link mentioned in comments below, some of it is quite, well, racey for the BBC! (Although the delivery of some terms, like the wonderful ¡Hostia! is rather tame).

Meanwhile Jergas de Habla Hispana is an interesting project, trying to bring together all the slang from all the Spanish speaking countries around the world. The interface is slightly confusing, but there’s a lot in there, just check out all the ‘C’ words in Spanish!