even though this plugin has already been around for a while, I've never posted about it here.
You may be interested in this helpful shipping rate computation method, which lets you define regional zones (by country, province, zip codes) and weight ranges.
You then edit shipping rates by simply clicking on the Zone/Weight table.
Zones and ranges are specific to shipping methods, so you can customize zones, ranges and rates for different couriers.
Finally, you can also configure a minimum order subtotal, or a free shipping per each zone.
You can give it a try for free with a 2-zones and 2-weight-ranges limit: download from here.
Also, feel free to provide feedbacks and improvement ideas.