As centers of innovation go, there are worse places to place a bet on the past repeating itself than California's technology hub. Looking beyond the Internet, housing and credit bubbles, it's still the preferred playground of such leading financial weathervanes as venture capitalists, gizmo nerds and software studs.

Perhaps Wall Street, searching for reasons to remain optimistic about the market's summer rally, should take heart from the spate of articles painting pictures of green shoots all over Silicon Valley. The Wall Street Journal's Deal Journal notes that tech IPOs are staging a comeback, and asks if its time to party like it's 1999?

Our reporting shows that investors, encouraged by a growing number of acquisitions and public stock flotations in the past few months, are keeping a close eye on a coterie of promising startups in Silicon Valley. David Lawsky identified six privately held companies as the ripest for acquisition or readiness to go public, out of 34 cited in industries ranging from alternative energy to social networking.

The top four are business social network LinkedIn, solar panel maker Solyndra, smart grid company Silver Spring, and Zynga, a casual games company whose products run on social networks like Facebook. Two others are Guidewire, which makes software for property and casualty companies, and LiveOps, which runs call centers using private contractors who work from home.

But he reports that the Silicon Valley Six say they intend to keep growing organically rather than agreeing to be acquired or go public during the recession. Recession or no, there is clearly plenty of money looking for a ride. That's the thing about bubbles; they tend to be more fun when you catch them early.