I’m just wondering if there is a small-number-of-clicks way to prevent some part of the mesh, e.g. a particular vortex group, from rendering while I work on the mesh and do test renders? I don’t want to make them a separate object or anything, just “get them out of the way” like I can hide them in Edit Mode, then switch their visibility back on later. Is there a setting for instance for not rendering anything hidden in Edit Mode? (The answer to that is no, right? 
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Add selection to a vertex groups and use a Mask modifier with display modifier in viewport disabled
http://wiki.blender.org/index.php/Doc:2.6/Manual/Modifiers/Generate/Mask