Our host, Adagio, has a very nice basic ceylon, and generally very good pricing as well. http://www.adagio.com/black/ceylon_sonata.html?SID=4f920bfe33097f85214d30c685993a74
I've gotten loose leaf black teas from places like Upton, Harney & Sons, SpecialTeas, New Mexico Tea Company... all were fine, none were better or more affordable than Adagio. I go to specialty-type companies for certain teas like Japanese greens, first-flush Darjeeling, and certain oolongs, but I find Adagio is a great place to buy staples and explore new types of tea varietals. I highly recommend the various samplers they have... it was a great introduction to a new world of tea for me.