On Thursday — the first day of trading after Facebook filed for its IPO — investors went into overdrive. Here’s a look at the gains in social stocks yesterday: Company Ticker Price Gain Zynga ZNGA $12.39 +17% Groupon GRPN $23.08 +7% LinkedIn LNKD $76.98 +6% Pandora P $13.32 +3%

It’s a good bet that some of the moves came from short covering. This means short sellers — who are betting on a stock price to fall — were closing out their positions, which involves buying back stock. It adds even more fuel.

At the same time, the Facebook filing shows how the company is certainly the uber player in the space. Take a look at the recent financials (these are annual figures as of the third quarter of 2011): Read 

On news of the Facebook IPO filing, top social stocks – like Zynga (NASDAQ:ZNGA), Groupon (NASDAQ:GRPN) and LinkedIn (NYSE:LNKD) – are soaring in today’s trading.

But online gamblers are also getting  a piece of the action. On Europe’s largest betting site, Paddy Power, you can wager on the IPO price of Facebook (the press release had a great title:  “He’s No Zucker”).

So far, the favorite range is $35 to $44.99. Although, some betters think a price of $65 or more is possible. Read 

Rick Marini is one of the pioneers of social networking. Back in 2002, he co-founded Tickle, which grew to 200 million registered users and $40 million in revenues. In 2004, he sold the company to Monster Worldwide (NYSE:MWW) for $100 million.

His next gig? Another social company, BranchOut. The company leverages Facebook to help users connect to find jobs and other business opportunities. Essentially, it is similar to LinkedIn (NYSE:LNKD).

Since the beginning of 2012, BranchOut has grown its active user base from 920,000 to 2.7 million. Customers include Salesforce.com (NYSE:CRM) and Microsoft (NASDAQ:MSFT). Read 

In 2000, Alex Mehr came to the United States from Iran to find better opportunities. He wasted little time — besides earning a doctorate in mechanical engineering, he worked at NASA for a couple years.

Then in 2007, Mehr joined Shayan Zadeh to create Zoosk, with a focus on the Facebook platform. Since then, they have raised more than $40 million in venture capital and have attracted more than 50 million registered singles. Last year, the revenue run-rate was $90 million. And the Zoosk Facebook page has over 6 million “Likes,” which is on par with brands like Yahoo! (NASDAQ:YHOO), Disney‘s (NYSE:DIS) ESPN and Nike (NYSE:NKE).

I recently had a chance to talk to Mehr about Zoosk, apps and the Facebook IPO: Read 

The following is an unedited letter from founder and CEO Mark Zuckerberg, filed with Facebook’s IPO paperwork:

Facebook was not originally created to be a company. It was built to accomplish a social mission — to make the world more open and connected.

We think it’s important that everyone who invests in Facebook understands what this mission means to us, how we make decisions and why we do the things we do. I will try to outline our approach in this letter. Read 

The social IPO of social IPOs is finally here.

In 2011, we saw some blockbuster social IPOs hit the market, including Pandora (NYSE:P), Zynga (NASDAQ:ZNGA), LinkedIn (NYSE:LNKD) and Groupon (NASDAQ:GRPN). But the whole time, investors really wanted to get a piece of Facebook.

On Wednesday after the bell, their wishes came a giant step closer to being granted: Facebook filed for a $5 billion IPO. Said founder and CEO Mark Zuckerberg in the letter accompanying the S-1 filing: “Simply put: we don’t build services to make money; we make money to build better services. And we think this is a good way to build something. These days I think more and more people want to use services from companies that believe in something beyond simply maximizing profits.” Read