Having spent my formative years in two major tea-drinking cultures, I drink tea at least once, usually two or three times a day. I'm fond of stronger, maltier teas -- usually some kind of Assam, or Assam-based blend.
My preferred mail order site in the US is Upton Teas. They're great for tea novices because you can buy 1 oz sample packs of any of their many, many teas. Black teas seem to be their specialty, but they've got a very respectable green and white tea section.
For sheer quality, nothing I've tried from them beats the offerings at HR Higgins im London, but I've run out of my smuggled tea hoard and shipping from the UK is rather expensive. Upton's CTC Assam in particular is superb value.
More recently, I've also been drinking less obvious Japanese teas like soba-cha, hoji-cha and roasted barley tea. The latter cold-brewed and served ice cold makes for an excellent summer beverage. I buy these at my local Japanese supermarket.