Uji (30 min south of Kyoto) is Japan's tea capital. Visit a tea house, try a matcha ceremony, and stock up on quality matcha to take home.
Tsuen Tea (since 1160) and Ippodo are the legendary names. Both have tasting bars where you compare grades of matcha.
Byodoin Temple in Uji (the building on the 10-yen coin) is a worthwhile pairing for a day trip.