I'm a loose leaf tea drinker, and I would highly recommend drinking loose leaf over just about anything else. I would not necessarily recommend a brand as much as I'd recommend getting acquainted with some of the fundamental types of tea. Once you do that, you will likely start to gravitate toward a certain style and type of tea and you can try different brands and suppliers to see which are your favorite.
Basic loose leaf tea types:
Then there are a few others that are not really tea, or else they are not based as much from steeping purely and actual tea leaves:
Some good places to order all the listed types of tea above would be adagio.com and specialteas.com.
I will be writing an actual hub soon, but I thought a shorter answer would be good in the meantime.