Techniques are described for facilitating performance of tasks by human users. A task exchange server system acts an intermediary to facilitate performance by human task performer users of tasks provided by other task requesters, such as by providing information about tasks via an electronically accessible site. The task exchange server may further cause information about tasks to be provided to at least some users as they interact with third-party sites not provided by the task exchange server, such as third-party sites operated by entities unrelated to the task exchange server's operator. The third-party sites may include information about tasks along with other information that the third-party sites provide to users, or instead a separate client-side program executing on computing devices of certain users may obtain and present information about tasks to the users, such as in conjunction with information provided by unaffiliated third-party sites.