A discussion on edstat-l concerned a statistic called p-rep. I had not heard of this statistic before, but at least one journal is calling for its use in all papers published by that journal.
There is a nice description of this method in a publication by Peter Killeen, and a detailed bibliography plus an Excel spreadsheet is available as a ZIP file.
This statistic sounds suspiciously like a post hoc power calculation, but I have not examined the formulas in any detail. When things get calmer here (they are never completely calm), I will try to describe this in more detail.
You can find an earlier version of this page on my original website.