More data is showing that the love affair between venture capitalists and Web 2.0 startups has come to an end – or, at least, that the ardor is fading. Meanwhile, “cleantech” continues to heat up.

Between July and September, venture investment in the sector dropped precipitously, to its lowest point since the middle of 2006, according to Dow Jones VentureSource.

However, a report from Ernst & Young based on the same VentureSource data, pointed out that investments in cleantech hit a record $1.6 billion in the third quarter. That total represents a 55 percent increase from one year earlier.

Seven of the top 10 venture deals in the quarter were in solar, E&Y noted. In all, solar deals generated $990 million in capital – and $1.7 billion for the year.

The cleantech deals indicate many of the startups are moving toward commercialization and need more capital, said John de Yonge, Ernst & Young’s Americas research director of cleantech and venture capital.

"We’re seeing these large follow-on rounds to solar companies to get them to that next stage," de Yonge explained.

During Q3, there were 23 web 2.0 investments (basically, investment in companies that tap into the web’s social and collaborative capabilities) totaling $220 million. That’s about a 47 percent drop from the $435 million invested during Q2, and a slightly larger drop from the $442 million invested during Q3 last year.

Of course, one quarter doesn’t make a trend. And even if it the drop continues, for now it has only fallen to 2006 levels, not dropped off completely.

Still, Web 2.0 companies hoping for funding should be particularly worried, since this data doesn’t show the effects of the recent financial turmoil (which hit at the end of September), such as the resulting liquidity issues among VCs.

The latest MoneyTree Report from PricewaterhouseCoopers and the National Venture Capital Association shows a similar drop in Internet investments, with much of the money moving to other sectors like cleantech and biotech. And even at the Web 2.0 Summit last week, a lot of the discussion revolved around the recession – the outlook isn’t very positive.