We wonder what her kids think of all this!

Madonna recently joined Instagram, and the pop singer hasn't wasted any time uploading personal photos that show her in various states of undress! Even though she's in her 50's, Madge sees no problem with showing off her sexy bod, apparently!

In her latest post, the Grammy winner shows off her enviable backside in a picture taken backstage before one of her concerts. In another snapshot earlier this week, the mother-of-four showed off her cleavage dripping with sweat after a workout. Yikes!

Not all her updates are of a sexual nature, though!

The blonde bombshell also showed off a Valentine's Day card from one of her kids that read, "Happy Valentine's Day. You are the best and you make me so happy. I love you Mom."

When you are the Queen of Pop, you can do - and post - whatever you want!

Nothing gets in the way of Brad Pitt and his uber-expensive motorcycle collection.

The A-list daddy of six hit the road in Hollywood riding his brand new custom Ecosse Titanium Series XX bike worth more than $300,000!

According to Ecosse's website, the "two-wheeled creations are built to the highest standards, using the most exotic materials in never-before-seen designs. The firm already has the honor of being the maker of the world’s most expensive motorcycle."

Sounds like the perfect piece of machinery for Angelina Jolie's fiance.

Nicole Kidman may be a busy actress, but the gorgeous redhead always has time for her main man Keith Urban.

The lovebirds left their daughters at home for a romantic Valentine's Day dinner at Eveleigh in Hollywood.

With her hubby on the judges' panel for American Idol, we can't wait to see Nicole in the audience!

She's never looked better!

Jennifer Love Hewitt covers the March issue of Self, and the TV actress looks smoking hot in a bright pink bikini as she shows off her the results of her new diet and workout routine!

After those famously unflattering bikini shots of her in Hawaii hit the Internet in 2007, the Client List star decided to take control of her health and whip her body back into shape.

'I wasn't going to the gym or eating right when that unfortunate photo was taken. It was time to start working out and watching my diet more closely," she confessed to the mag.

The former Party of Five actress credits her new and improved figure to a yoga/dance combination called Buti, as well as wearing ankle weights on her downtime and adhering to a strict diet.

Her rumored new man Brian Hallisay must be smitten!

Gwen Stefani rocks killer style ... even when she's not trying!

The No Doubt songstress led her boys, Kingston and Zuma, through LAX with the help of a punk rock-looking assistant. Love it.

Let's hope the blonde "Don't Speak" singer was on her way to meet hubby Gavin.

She never misses a workout!

Kim Kardashian attended her daily workout this morning, and we can't help but notice her ample assets! Pregnancy is causing her chest and hips to get bigger by the day, and it's making her baby bump look nonexistent by comparison!

The reality star and boyfriend Kanye West enjoyed a romantic Valentine's Day meal at Lawry's Steakhouse in Beverly Hills last night, so the brunette beauty was probably eager to work off the extra calories!

Kimmy K's decadent dinner might have also doubled as an early celebration, since former husband Kris Humphries' lawyer Marshall Waller dumped the basketball player as a client hours before a joint court appearance today.

It appears Yeezy's lady love might be granted the divorce she's been hoping for once and for all!

This is simply adorable!

Vanessa Lachey released a heartfelt journal entry dedicated to son Camden, and clearly motherhood was made for her!

"This Valentine's Day you'll be five-months-old, but I feel like I've loved you forever. I have wanted to be your mommy for as long as I can remember. Nothing in this world could ever compare to the way you make me and your daddy feel everyday!" she wrote in the message.

Aww!

"Words don't even begin to express how much more beautiful you make our life together. As you grow and take in this world around you, know that you are loved today and EVERYDAY all because you're you! Sweet precious little you," she added.

The former model began keeping a journal for her future children when she married Nick Lachey, and she hopes that one day it will be a meaningful memento for her brood.

"I wrote about how Nick proposed, our wedding, our first home as a family, our adventures together, and how we are as people and as a couple. Once I got pregnant, I started writing letters to our unborn baby. I would tell him how loved he is and how excited I am to share EVERYTHING in the world with him," she explained.

Little Cam is lucky to have such a thoughtful mama!

Looks like Katy Perry and beau John Mayer may be tying the knot soon. Check out her ruby red ring ON her ring finger!

The sexy crooner reportedly popped the question to the "Fireworks" singer last night while the two enjoyed a sexy Valentine's Day dinner date at Vincenti in Brentwood.

Katy was all smiles while leaving the restaurant with her man, and of course, she couldn't help but show off her shiny sparkler!

The night before, Mayer and his ladylove hit up Katsuya in Brentwood for a sushi date. Wow ... these two have been inseparable!

Wonder what Perry's ex Russell Brand thinks about her settling down with Mayer?