At present, we do not have a method to offer buyers a selection of shipping services, nor do we currently integrate with UPS or FedEx for live rate-lookups.
If you do not want to use the US Postal Service live rate-lookups we do currently support, then you can configure a custom shipping calculation method. You may find it helpful to know the basic formula we follow when calculating shipping charges:
(rate X (total product wt. + container wt.)) + (container cost) + (handling cost)
Note that you can "game" the formula by applying non-literal figures for various settings, so the formula adds up the way you want. See some examples on our Shipping help page here:
http://www.e-junkie.com/ej/help.shipping.htm