I first came across mate when I was studying abroad in Poland. My roommate was from Argentina and she brought some with her to share with us. If you read the wikipedia page I linked to, you'll see there is a culturally appropriate procedure to drinking mate. Unfortunately, I am totally not following that.
But this was on sale at Whole Foods a couple weeks ago:
It looks a little weird and the longer it sits, the greener it gets (which I found out after leaving half of a cup sitting out all day). Overall, I have been plowing through my bag of mate. The earthy taste is delicious and its a great pick-me up for early morning study sessions. I brought it with me since we will be in Michigan this week, so I can enjoy it every morning and not have to worry about scrounging for some really old tea in someone's cupboards.