Kim Kardashian posed with her fiancé, Kris Humphries, at a Matthew Williamson fashion show in Monaco today. She looked gorgeous in a white dress for the occasion, but it was Kim Kardashian's huge diamond ring that was the center of attention. Kim's been flaunting her new 20.5-carat accessory since announcing her engagement to Kris with a People cover on Wednesday. She flashed the sparkler at the airport on her way overseas, and it looks like she's already starting to plan her nuptials. Kim tweeted a picture of her two youngest sisters, Kylie and Kendall, and asked, "how adorable are my bridesmaids?" The newly engaged couple haven't shared any other details about their wedding, but Kim's mom, Kris Jenner, did request that they give her a little more time to plan than the nine days that she had to pull Khloe's event off.

Justin Bieber held on tight as he planted a big kiss on girlfriend Selena Gomez in Hawaii on Thursday. The two have been all about going public with their PDA, and Justin Bieber also kissed Selena Gomez as he headed up to the stage to accept a statue at last Sunday's Billboard Awards. After the show in Vegas, the two were off on this romantic getaway in Hawaii where bikini-clad Selena Gomez and shirtless Justin Bieber wasted no time hitting the beach together. The young couple have a chaperone with them for the trip, his mom, who was along when they went paragliding in the afternoon. Still, that didn't stop them from getting especially hot and heavy in the ocean, where Selena straddled Justin for another makeout session.

Sarah Jessica Parker and Matthew Broderick had a little help packing up their car outside of their NYC home earlier this week. They loaded their trunk and took off with the whole family, including their adorable twins, Tabitha and Marion. SJP recently returned to the Big Apple after a trip to France for the Cannes Film Festival, but she's already back into the swing of things. She's been taking care of the school run with James Wilkie and stepped out for a Broadway show with Matthew and pals Naomi Watts and Liev Schreiber. SJP will soon be adding press to her plate for her September movie, and the first I Don't Know How She Does It trailer was just released. The busy mom will hopefully have a chance to relax with her crew during the long weekend, and we hope you all have a fun and safe Memorial Day too!

Rihanna was on The Today Show bright and early this morning in NYC, sporting a skimpy uniform as she sang several of her latest singles, including "What's My Name" and "California King Bed." She was fresh off a performance with Britney Spears at the Billboard Music Awards last weekend. The pop stars joined forces to perform their "S&M" remix in matching leotards and even shared a near-kiss, and while some thought the routine was a bit too steamy for TV, Matt Lauer admitted to watching the video several times! She and the morning-show hosts shared a few laughs in between her songs, but things took a slightly scary turn when an overzealous fan grabbed Rihanna while she belted out one of her hits. The star was unhurt, and her backup dancers quickly came to her rescue to help her wriggle free.

Gisele Bundchen brought her son Benjamin and stepson Jack to a park in LA yesterday. Ben was absolutely precious in his mini hat and dapper button-down while big brother Jack showed him the ropes on the slide. Then all three kicked off their shoes to play in the sand. Both boys look like spitting images of their dad Tom, who missed the sunny afternoon outing. It has been a very fun-filled May for the Bundchen-Brady clan, since just last week Gisele wore a bikini and Tom Brady was shirtless for a waterslide romp in Mexico. Gisele always looks fantastic in her skimpy two-pieces, which is just one reason she's ranking high in the PopSugar 100 sexiest female celebrity list, though there's still time for her to climb the ranks from her current number six spot.