Steap Tea opened relatively recently (perhaps in Winter 2005/2006?) a bare street north of Rittenhouse Square on 18th, apparently relocating from Wayne, where it was known as the Wayne Tea Salon.
It sells quite fragrant tea, with a great selection of the rarer greens, oolongs, and whites, along with flavored blacks, chais, and other more common varieties. Prices are comparable to online merchants such as Adagio, placing them at an extremely reasonable price range. Their teaware is quite nice as well if a bit more expensive, including the last of the Jeaner line.
My one complaint? Although they offer tea in their store, it's in paper filters and cups - then again, if the tea is right, who minds its container?