Yes, a private group to share ideas and motivation could be useful and I'd be willing to be involved. Could be very low-tech too - just IM/email and some FrieNDAs.
I'd like to share two techniques I've found somewhat helpful (though not quite the ultimate answer, unfortunately).
1. While side projects often have no deadlines and thus less motivation, employees don't really have the same problems. I've delegated more components from side projects to my employees and the result is things getting done much faster. Now the progress block is things that are back in my hands - writing content, taking a working product and launching it for people to try.
2. A while back, an entrepreneur-type I know over the net and I did an experiment. We would both work all day and struggle with motivation to complete site-projects during the evening so we decided we'd each complete a small site project in one week. Each morning, we'd check in to show our progress. Failure to show progress meant the other person was to apply guilt trips were appropriate. Monday night as planning, Tuesday was fleshing out content, Wednesday was a skeletal site, Thursday was putting things together, Friday was polishing and making it live. Each night, the pressure of thinking you'd have nothing to show the following morning was enough to force productivity. On nights when I'd normally laze around or procrastinate at the desk, I'd cram 1-2 hours of work around or after midnight. It was enough to get a basic site rolling by the Friday that I would never have otherwise done. It worked for me but unfortunately the other guy didn't get going quite as well. Still, I'd do it again.
