I have Magento 1.8.1. I wanted to know if I could share the same 3 Simple Products with 2 different Configurable products. And if this is possible how would I go about doing it.?
This is fine as long as the configurable options on the simple products are unique per configurable product.
You can add the same simple to as many configurable products as you like - but you can't add two simple products with the same size, for instance, if size is the configurable attribute.
Is that what you were after?
In regards to achieving it - just log in to admin, create a configurable product and start adding the simple products to it. When you're in the tab that allows adding simple products, you will see that when you select one simple product - say size 'S', all other simple products with size 'S' will be greyed out and you won't be able to add them.