I had put this together for a client a couple of months ago, and I'm just getting around to blogging about it now, at the time I couldn't find any tools that might make this task easier, I assume folks who build web stats analyzers will deal with the S3 format natively, eventually.
Until that time, here's a little converter to make Amazon S3 logs understandable to your favourite web log analyzer.
The work is done by one gnarly regular expression, which was easy to put together with the help of Pyreb.
You can download the python source here, and as always your mileage may vary.


