As some readers will know from earlier posts, and perhaps as participants at past events, I help organize the Renewable Energy Business Network, or REBN. Last night more than 400 clean energy professionals came out to an event we organized at the Cleantech 2008 conference, and co-hosted with the New England Clean Energy Council, the U.S. DOE's Energy Efficiency and Renewable Energy Program, and the American Council on Renewable Energy. A great indication of the level of interest in this industry right now, and of the desire those in the market have for being able to connect with each other. We used the event to announce some major changes for REBN, which has now been incorporated as a national non-profit organization dedicated to helping clean energy professionals make those connections, for learning, sharing and collaboration. REBN is also rolling out chapters nationwide, with chapters now up and running in Boston, San Francisco, Houston, Austin, Denver, Seattle and New York, and with others in formation in other places across the country. REBN will also be developing some cool web-based and event-based efforts down the road as well.  [Update:  see press release here] The REBN expansion story is really indicative of what's been going on in this market. REBN was originally started around seven years ago by a group of renewable energy professionals (such as Josie Gaillard Taylor and Dan Kalafatas, among others) in the San Francisco area. Their low-key, informal networking approach attracted others among their colleagues, and over time the group grew into a good regional effort. Last year, Andrew Friendly and I launched a REBN chapter here in the Boston area (I'd been helping to run REBN out in SF before moving east), to try to help bring people together in the same way. The response was immediate, as the group's informal, come-as-you-are approach seemed to resonate with the Boston cleantech community in the same way as it had in the SF community. And as we chatted with people in our broader networks about our experiences, others started approaching us about launching REBN chapters elsewhere, so that chapters were spontaneously starting up in places like Austin and Denver. At which point formalizing the organization and facilitating that organic expansion started to make a lot of sense. The organization now has nearly 2,000 members across these chapters, and with the national expansion that's already growing quickly. This overwhelming wave of interest, largely over the past year-plus, across the country, is really indicative of the overall level of business, researcher and entrepreneurial interest in cleantech right now. From an investor's perspective, that's a phenomenal sign. It says the industry has hit an inflection point, where great ideas are attracting great people with more great ideas. Perhaps the most telling anecdote last night was the conversation I had with one inventor with an energy-related startup effort. As he was telling me about his startup, I mentioned another similar effort I'd seen recently. This entrepreneur then pointed at another REBNer a few yards away, and explained that that entrepreneur ALSO was working on related technologies. They'd just met at the event that evening, and were already figuring out to work together to take their efforts to the next level, jointly. That's what REBN's all about.