From SCOTUS Blog, which has a nice photo in addition to a full write up:

With President Obama and Vice President Biden and some 450 other witnesses looking on silently, Justice Sonia Sotomayor took her seat for the first time on the Supreme Court bench Tuesday afternoon, the 111th member of the Court in its history.  Among those attending was her predecessor, retired Justice David H. Souter.  The event was so well attended that the Court opened the velvet curtains at the rear of the chamber, to allow for some spectators to stand.  (The transcript of the proceedings is here.)

Tomorrow Justice Sonia Sotomayor will hear her first argument as a member of the Supreme Court, the Citizens United case (.pdf) involving a challenge to the decades old ban on corporate expenditures in federal elections. As the folks at First Read not, it will be awfully difficult for conservatives to rail against judicial activism should conservatives on the Court push a radical rewriting of the law to bar Congress from placing reasonable limits on the expenditure of unlimited corporate funds in elections.