1. A system, comprising: an image processing and on-demand pickup dispatching service being capable of data communications over a communications network, the image processing and on-demand pickup dispatching service being configured to: maintain shipping information for a plurality of previous shipments, the shipping information including information that indicates at least a shipping company that shipped the previous shipments, the shipping information further including package weight, a package dimensional size, an origin location, a shipping destination, a transit time, a service level, and/or shipping price for some or all of the previous shipments; maintain user information for a plurality of users, the user information including user identification information for enabling the image processing and on-demand pickup dispatching service to exchange electronic communications with users, the user information further including payment information for enabling the image processing and on-demand pickup dispatching service to collect payment from users; and maintain courier information for a plurality of couriers, the courier information including courier identification information for enabling the image processing and on-demand pickup dispatching service to exchange electronic communications with couriers, the courier information further including courier capacity and location information; and a location-aware, network-connected handheld user device, including: an image-capture component for capturing a digital image of an item to be shipped; a location component for determining location information that corresponds to a location of a user; a communications component for facilitating data communications over the communications network; a user-input component for receiving user input; a user-output component for providing visual output; memory for storing executable instructions; and a processor being provided in communication with the image-capture component, the location component, the communications component, the user-input component, the user-output component, and the memory; and an on-demand shipping client application being stored in the memory of the handheld user device, wherein the on-demand shipping client application, when executed by the processor of the handheld user device, is configured to: output, via the user-output component of the handheld user device, at least one graphical user interface that enables the user to provide, via the user-input component, user input that: causes the image-capture component of the handheld user device to capture a digital image of the item to be shipped, the digital image being captured prior to packaging of the item; and corresponds to a shipping destination for the item to be shipped; query the location component of the handheld user device for location information that corresponds to the current location of the user; and output, via the communications component of the handheld user device, the digital image of the item to be shipped, the user input that corresponds to the shipping destination, and the location information that corresponds to the current location of the user; the image processing and on-demand pickup dispatching service being configured to: obtain from the handheld user device, via the communications network, the digital image of the item to be shipped and the location information that corresponds to the current location of the user; use a digital image processing component to process the digital image to determine a physical characteristic of the item to be shipped, the physical characteristic including a weight and/or a dimensional size; query the courier capacity and location information to identify a courier from the plurality of couriers, wherein the courier is identified based at least in part on a capacity to handle the physical characteristic of the item to be shipped and the current location of the user; transmit to the courier, via the communications network, a dispatch notification that includes the digital image of the item to be shipped, information that indicates the physical characteristic of the item to be shipped, and information that indicates the current location of the user; and receive from the courier, via the communications network, a courier response that indicates whether the courier accepts or declines the dispatch notification, wherein the courier response is based at least in part on an evaluation of (i) the item to be shipped as represented in the digital image that was captured prior to packaging and (ii) the information that was determined using the digital image processing component and that indicates the physical characteristic of the item to be shipped, wherein the evaluation of the item as represented in the digital image enables the courier to at least partially verify (a) the information that was determined using the digital image processing component and/or (b) that the item does not include an irregular dimension for which the courier would not have capacity to handle.