FYI, Galangal freezes very well, the powdered and dried stuff are not worth your efforts. As mentioned above, many Asian grocers will carry it.
Kaffir Lime Leaf powder and its dried version have nothing to compare with the fresh or frozen type. It lends a nice light tangy and aromatic taste to dishes. It is added to many soups and stocks, much like you would use a Bay Leaf, shredded it can be added to Lao Larbs and other SE Asian dishes, sometimes it is deep fried and used as a garnish.