I do business on the internet and I use a flat rate that I have calculated based on averages. I am really "out of business" and trying to be retired, (no longer advertizing) but occationally I have people that still ask for help.
I am of the personal opinion after using the internet for business and shipping product for over 10 years that the best way is to set a basic rate, and put it into the price you are asking for your product.
LL Bean just started to do this and it makes it a lot easier to purchase product from them. "Free shipping" has the attraction that the customer knows exactly what he will pay. tehn link optional "fast" shipping to the USPS, UPS, or FedEx calculator. If you live in town and have a lot of business UPS and FedEx will set you up. If you live out of town, or do not ship that large a volumn, USPS "Click-N-Ship" priority mail works really well. I have used USPS "Click-N-Ship" ever since they started the program about 6 or 7 years ago. (however, there are some things you cannot ship using USPS, fortunately none of my work is in one of those catagories)