Can I participate in trading Facebook shares on their IPO day from any brokerage?
Any retail equity brokerage will give you access to the NYSE, and thus Facebook shares as they become available.  However, it is important to note that you nor any retail investor will be able to purchase FB at the IPO prices ($33-38 IIRC).  The only people who will be able to buy in at that price are the underwriting investment banks and major investors who have subscribed to the IPO.  You, and all the other retail investors will only be able to buy in as those major investors offer shares on the secondary market.   This being Facebook, there will probably be a significant premium over the IPO price, both due to demand and systemic underpricing of IPOs to encourage the opening 'pop'.   So, if you're intent on buying in at the IPO, pay close attention as the date approaches.  Look at how the recent big IPOs have performed (GRPN, LNKD come to mind).  Know how much you're willing to commit and what price you want.  However, no one is going to know what the opening market price will be come Friday morning.  Be watching your financial data source / analysis of choice and be prepared to make a judgement.