Standardization efforts will eventually provide transparent access to multiple grid service implementations. Necessarily, the standardization is a slow process that requires consensus from developers of the various service implementations. Users, however, cannot wait for the consensus to appear before running their applications. Consequently, they seek various mechanisms to shield them from service API changes and to allow them to use the maximum number of resources. This session will review some of the mechanisms that are currently used, how those are accommodated on the EGEE infrastructure, and the status of some proposed standards. These mechanisms include web portals (GridSphere, P-GRADE, GENIUS), standards based services (GridWay, Taverna, MOTEUR), and high-level APIs (GANGA, SAGA).