A machine readable code (e.g., digital watermark or bar code) conveyed with objects is used in establishing links to associated electronic resources, such as web pages. The object can be physical (e.g., a magazine page) or electronic (e.g., music data). The associated electronic resource can be a web site from which goods or services (e.g., music) may be offered for sale. In some embodiments, when a code is sensed from one object, the system can foresee other object codes that may soon be sensed, and can anticipatorily provide address information for their respectively associated electronic resources. In another embodiment, the microphone of a cell phone is used to listen to ambient audio. A watermark in the audio is decoded and its payload is used to link to, or provide, related information. A variety of other concepts are also detailed, such as permitting the free distribution of low fidelity music as marketing agents for higher fidelity versions that are available for sale.