Oh Snap!

Mischa Barton steps out with a mystery guy to London hot spot Umbaba recently, fueling rumors of a breakup with rocker beau Cisco Adler.

Mariah Carey puts herself in a number of good hands during her Adventures of Mimi tour, which kicked off in Miami on Saturday.

Lance Bass stops by ex-bandmate JC Chasez’s 30th birthday party in West Hollywood on Sunday. Bass, who attended with boyfriend Reichen Lemkuh (inset), also caught up with former ‘N Sync-ers Justin Timberlake (who arrived with Cameron Diaz) and Chris Kirkpatrick at the bash.

Jack Black plays human swing to his slumbering 1-month-old son during an outing in Santa Monica on Saturday. The actor gets back to funny business in September, when he begins filming the comedy Be Kind Rewind opposite Kirsten Dunst.

Costars Teri Hatcher and Eva Longoria hold on to a funny moment at the DVD release party for the second season of Desperate Housewives in Universal City, Calif., on Saturday.

Looking post-partum fabulous, Rachael Weisz has an outing with 9-week-old son Henry (with director Darren Aronofsky) in New York City’s SoHo neighborhood on Friday.

Julia Roberts, who is sitting out filming Ocean’s Thirteen this time around, uses her downtime to run errands near Venice Beach on Sunday.