Lots of great FAQs over on the Composting forum. Including what to add and what not to add. And it is a very active forum too.

Fruit pits are fine but they take forever to break down. The chemicals in fruit pits are only poisonous if ingested. It isn't as if your compost will later grow cyanide plants. :)

Dave

Here is a link that might be useful: Composting Forum

It is pointless to put in fruit pits as one year later they will look exactly the same, same with olive pits or anything else equally hard

I will be putting them into a hugel garden, so it would add aration to the hugel. Thanks anyway.