Does anyone know an equivalent to the MovableType plugin FieldDay(https://github.com/movabletype/mt-plugin-field-day/wiki/Basics) for Magento. I need to be able to create multiple instances of product field sets. (i.e. multiple instruction blocks)
You need to create a custom attribute, with a custom renderer.
You will find here an example about how to create an attribute that supports a custom renderer with 2 fields. You can extend that to support a dynamic number of fields.
You can also take a look at how the tire prices functionality is built. I think it's similar to what you need.
Magento allows to have multiple custom product fields (attributes) per product. See admin > catalog > manage attributes > attributes
As in one store you can sell different type of products, with different fields, magento allows for each product define it's own attribute set. See admin > catalog > manage attributes > attributes
When you creating or edit attribute, you can specify "Show on Product View Page" to be "Yes".