Magento SKU Auto Generator Pro extension is best solution from UsCoding. It helps website owner can create SKUs for products automatically.
This extension is ideal for stores that create auto number SKU for product or create product SKU from category SKU. That means you have two types for create Product SKU.
With simple extension's configuration, you will have perfect additional feature in your store.

Product detail: uscoding.net

Main Features
- Create Auto Numeric for SKU codes
- Set a Prefix or a Suffix string for your SKUs
- Allow to use SKU prefix from Category and build SKU for Product
- Enable or Disable SKU auto generation
- Easily to install and config