Facebook's much-publicized first sale of stock to the public started with a bang and then cooled a bit this morning as the social media giant's share price immediately rose from $38 to about $42.50.

The 12 percent rise just after 11:30 a.m. ET highlighted one of the most-anticipated debuts on Wall Street in decades.

But minutes later, the stock had settled a bit and was trading around $40 - still a 5 percent gain over the initial offering price of $38.

We'll keep an eye on how the stock is doing, and watch for related stories of note, and update this post as the day continues.

Our original post and earlier updates follow:

We've told you it's coming. We've told you the initial price will be $38 a share. And we've said it's not going to be easy for regular folks to get the stock at that price.

Now, all everyone can do is wait for social media giant Facebook's first public offering of stock to hit the market.

Things will really get going, as The Deal Journal blog reports, around 11 a.m. ET. That's when Nasdaq expect to release Facebook's 421 million shares for trading.

We'll keep an eye on how trading goes and update with news as the day continues. We're also embedding a widget that should let us track the stock (trading symbol FB).

Meanwhile:

— NPR's Steve Henn wrapped up the news and previewed the IPO on Morning Edition.

— There's a Facebook "timeline" here.

— The New York Times put together an interactive graphic about how the Facebook IPO compares to other companies' debuts in the market.

Update at 11:30 a.m. ET. It's Trading; Opens Around $42.50 A Share.

Update at 11:18 a.m. ET. Still On Hold, And Some Are Concerned:

"This is getting a bit worrisome. Still nothing more than 15 minutes after Facebook was supposed to start trading," The Wall Street Journal's Steven Russolillo writes. "Nasdaq CEO Robert Greifeld told WSJ the exchange was 'well prepared' for the start of trading. We'll see."

Update at 11:02 a.m. ET. A Delay:

Nasdaq says trading in Facebook has been delayed at least five minutes.

Update at 10:45 a.m. ET. Anticipation Builds, Blogging Begins:

Various news outlets are firing up their live blogs. On its, The New York Times notes that Facebook's "$16 billion offering dwarfs the total capital raised by all I.P.O.s in the United States combined so far this year ($12.1 billion), according to Thomson Reuters data."

The Financial Times says traders expect to see "incredible volume today."

The Wall Street Journal's David Benoit is predicting the stock will open at $46.25.

Update at 9:35 a.m. ET. Zuckerberg Rings The Bell:

Facebook founder/CEO Mark Zuckerberg just set off the electronic bell that marks the start of NASDAQ trading for the day. But, remember, Facebook shares aren't supposed to hit the market until around 11 a.m. ET.