If you buy at a store, really check those sell by dates. Since most Americans don't like loose tea leaves, it doesn't have a high turnover in many stores.
I really like Ten Ren teas
http://www.tenrenusa.com/ . Even though good tea is expensive, it goes along way.
Have you tried a local Asian market? They tend to have a lot more tea varieties-look for the tea in a canister. Again, really check those sell by dates.