Patch/modification submission

Is there a format for submitting patches/modifications to existing apps? To avoid getting into trouble for cross-posting I won't mention the example in question, but there was an app that I had a fix for, and I added it as a comment to a thread discussing a problem that I fixed, then just posted to that thread, but I was wondering if there was a more centralized place for that kind of submission than the bottom of a thread buried in the "Other Apps" forum (where that unmentioned example is... and no, I'm not talking about P64, that I posted half an hour ago, I'm fine with where that one is).