Bitter Almonds

Brocho before eating this:

If the Almond is small and undeveloped: Borei Pri Ha'eitz

If the almond already ripened (not edible): No Brocho, unless sweetened and made fit to eat (where it would be Borei Pri Ha'eitz)

Brocho after eating the proper shiur of this: Borei Nefashos

Source: The Laws of B'rachos (pages 296, 297)

Also see: Almonds