'Extra' in the Capital!

Hollywood has officially invaded the nation's capital in anticipation of Barack Obama's inauguration!

Obama rolled up his sleeves and painted walls on this national day of service -- and sat-down for a pre-inauguration chat with Katie Couric. "There's enormous excitement about what's to come," dished Barack. Obama is feeling the pressure -- but revealed future First Lady Michelle is ready to step into the White House. "I think she is going to thrive -- she's going to be a First Lady America really gets attached to."

Barack's long-time friend Hill Harper is in on the inauguration action -- and invited "Extra" along for the ride! Harper joined Demi Moore and Ashton Kutcher, and the threesome spent today volunteering at a Washington D.C. high school, where Hill expressed excitement about telling Obama "how proud I am of everything that he's done."

Inauguration week in the capital kicked off with the We Are One concert, featuring performances from music bigwigs like U2 and Beyoncé. Samuel L. Jackson was just one of the celebrities honoring the future president at the bash, and told "Extra" the vibe backstage was one of excitement! "There were a lot of people that were just so amazed that we were in this particular space in this particular time, being a piece of history."

Jennifer Lopez echoed Jackson's feelings about the historical event to "Extra," saying, "It's a true honor to be here." The actress/singer joined hubby Marc Anthony at the Latino Inaugural Ball, where Anthony performed.