Feijoa tastes like a combination of pineapple and strawberry and is used in fruit salads. It is also known as the pineapple guava, due to its taste.  It is a gray-green , egg shaped fruit that is native to South America. Feijoas have also recently enjoyed commercial popularity in New Zealand, and are now being planted commercially in California as well. 

Feijoas are 2 1/2 to 3 inches in length, an olive green skin and have a pale yellow flesh that is very aromatic and sweet. They are juicy and very similiar to guava. They have tiny seeds in the soft inner pulp that are edible. The skin is thick and waxy and not edible raw, however it can be used in pickles and preserves. Feijoa are usually found hard and unripe in the produce market. Purchase and keep Feijoa in a dark, room temperature place till ripe. When ripe, keep in 38-45 degree refrigeration. Can be stored up to four days.  When ripe, the Feijoa becomes soft like a ripe plum, and has a pronounced aroma.

Eight to ten Feijoa yields one cup pulp.

Feijoas have a good amount of vitamin C and at 35 calories per fruit, are a good low calorie treat. 

Here are a couple of good links:

http://www.crfg.org/pubs/ff/feijoa.html

http://www.agroguias.com.ar/feijoaing.htm