I use a workflow to standardize state names which then allow me to fill out lead profiles with other details like region and sales representative. The workflow is triggered whenever a new lead is created OR a state name is changed. Each step looks for all the common abbreviations and missspellings I could imagine for a specific state (ex. for Illinois: IL, ILL Illinoise). The final step in the workflow assigns leads whose state names don't fit to a static list that I review monthly.