1. A system, comprising: a plurality of computing resources of a provider network; and one or more computing devices configured to implement an application streaming service, wherein the application streaming service is configured to: receive user input comprising a selection of an application by a user, wherein the user input is received at an access address from a computing device associated with a client of the application streaming service, wherein the access address is associated with an access environment, wherein the access environment permits access by the user, wherein the access environment is associated with an execution environment for the application, and wherein the execution environment specifies a computing resource description and an application source for the application; initiate execution of the application using one or more computing resources provisioned from the provider network and compatible with the computing resource description, wherein the application is installed on the one or more computing resources using the application source; and stream pixel data to the computing device associated with the client, wherein the pixel data represents a user interface of the application executing using the one or more computing resources.