What's the etiquette on prompting agents for a reply if you haven't received an answer to your query? Do you write them a nudge note? Well, most agents will specify a response time on their website/agent listing, so use that as a guide. Some of them will say something to the effect of "Don't call us. We'll call you." Keep writing and querying others in the meantime.
Miss Snark, in her own, inimitable way, gave great advice on this topic. She hates the nudge, but I wonder if she could have resisted this little gem.