Hi,
I can't claim to have read every single post in this topic, but I just thought I'd add my little bit. In my experience electrolysis is a pretty slow way to make H2, with pure water and a low voltage (<200). A few things to speed it up:
Add H2SO4 to the water, it souldn't get used up in the reaction (so you can just add more water and you've still got the sulphuric acid in there). This will increase the conductivity of the water, more current flowing for a given voltage.
Increase surface area of electrodes. My chemistry teacher once put Iron rods into accid for a while until they became pittted, then coated them in a silver compound (some cheap jewelery chemical stuff?) so they didn't corrode during the process.
Also, this is unconfirmed, I've never tried it, but apparently, chopped DC can increase the speed of the reaction (much like using ultrasonics). Off the top of my head, in certain 'pseudo-science circles', the frequencies are 600Hz (well not 'hertz, but cps), 610, 12Khz, and 40-42Khz. I did see this process on an episode of 'equinox' on CH4 in the UK, where guy used a small motorbike battery, a circuit, and produced enough H2/O2 to make a small implosive welding flame (3 inches). As I said, unconfirmed, and I haven't seen any evidence for this, so god knows how he actually did it (mains power from hidden cable?).
My £0.02, keelynet has lots of info on this, most of it anecdotal, but interesting none the less.
Good Luck.
Blueteeth