<p>I've just started developing an ExtJS application that I plan to support with a very lightweight JSON PHP service.  Other than that, it will be standalone. My question is, what is the best way to organize the files and classes that will inevitably come into existence?  Anyone have any experience with large ExtJS projects (several thousand lines).
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While developing your application your file and folder structure shouldn't really matter as you're probably going to want to minimize the release code and stick it in a single JS file when you're done. An automated handler or build script is probably going to be the best bet for this (see
http://extjs.com/forum/showthread.php?t=44158
).
That said, I've read somewhere on the ExtJS forums that a single file per class is advisable, and I can attest to that from my own experience.