Avocado seeds are edible.

http://omtimes.com/2012/10/13-great-benefits-of-eating-avocado-seeds/

13 Great Benefits of Eating Avocado Seeds

The Benefits of Avocado Seeds

By Dr Paul Haider
Everyone knows about Avocados… but did you know that Avocado Seeds are full of great health benefits?
Avocado Seeds have more antioxidants than most fruits and veggies on the market and polyphenols like green tea, plus they are full of more soluble fiber than just about any other food. — Wow!
In fact Avocado Seed has 70% of the antioxidants found in the whole Avocado, and Avocado Seed Oil is also full of antioxidants, lowers cholesterol, and helps fight off disease. And studies show that Avocado Seed has more soluble fiber than oatmeal and just about any other food. Avocado Seed helps to prevent cardiovascular disease, lower cholesterol, and prevent strokes.
Avocado Seed are great for inflammation of the GI tract and diarrhea too! In fact in South America Avocado Seeds are used for dysentery and other GI tract problems. Avocado Seeds has lots of phenolic compounds that help to prevent gastric ulcers, and prevent bacterial and viral diseases.
Avocado Seed contains a flavonol that prevents tumor growth… in fact studies with rats with cancer given Avocado Seed powder looks promising.
Avocado Seeds boost your immune system and keep you from coming down with debilitating diseases. Keeping your immune system high, because antioxidants keep free radicals at bay… and slows the aging process. Avocado Seeds seems to have a good anti-inflammatory ability and thus helps with arthritis and other joint diseases.
Avocado Seed Oil has been shown in studies to increase collagen in your skin thus helping to keep your skin looking young and wrinkle free. Avocado Seed Oil will make your hair shinny and help get rid of dry dead skin.


http://www.wisegeek.com/can-i-eat-avocado-pits.htm

Before you eat avocado pits, you may want to dry them. This can be accomplished by setting them on a dry, sunny windowsill. It will usually take several days for a pit to dry completely.
Avocado are stone fruits. This means that they have very hard seeds, or pits, similar to stones. Avocado pits must first be broken up or ground up into a powder before they can be eaten.
Tossing an avocado pit into a blender could ruin the machine. Instead, you may find that smashing it with a hammer makes it easier to grind it up. You can also cut the pit up before you grind it up.
To smash avocado pits before you grind them, put them in a heavy-duty plastic bag and smash them with a mallet or hammer. Putting a heavy towel over the bag will help prevent the bag from tearing. The avocado pit pieces can then be ground up in a heavy-duty blender or food processor. This should result in a fine powder.


http://www.onegreenplanet.org/vegan-food/why-you-should-eat-that-avocado-seed-and-how-to-make-it-tasty/

Simply take the seed from the avocado like normal and then knife it into quarters. This is much easier than it would seem. After that, the bits of seed can be thrown into a food processor, grinder or powerful blender to make powder. (Be sure the machine is up to the task). The resulting powder will be bitter and full of tannins, so it’s best use with other strong flavors, say in a green smoothie or juice, that’ll mask it a bit. About a half a seed is enough for one solid serving, and the other half can be saved for next time.