Well you could run a petrol generator with a little bit of work and a low pressure converter, or you can use it for anything you can use natural gas for. (low pressure already may need to adjust air/fuel ratio), gas lighting, etc etc.
You can do what William Gove did in the late 19th century...make electricity..(using the electrolyser for a poor mans fuel cell)
Here: http://www.ahanw.org/library/remotepdf.php?pdfurl=H2HOME%7e1.PDF
is a good article for reading from Homepower feb/march 1994 before you start. It discusses the use of electrolysers, and also makes mention that they produced 16v@10amps for a couple of hours (I assume before the electrodes used up their supply of bubbles on their surfaces.) This aspect requires further research, and just may provide some use for the dump power from oversize mills.
It also discusses the electrolyte you will probably be using, and its maintenance, as well as the use of arresters and bubblers and catylitic absorbers (to remove all traces of oxygen from the hydrogen gas stream)
It also gives graphs for the impurity risks as the current slows up, which will be useful to keep purity.
A worthwile experiment, and one I shall play with at a later date.
.............oztules