Today, pop culture entered a new decade -- Britney Spears celebrated her 30th birthday. Given that she's, you know, just about the most iconic female in the industry (you too, Beyonce), it's no surprise that her fellow stars wanted to send their well wishes. Both 17-year-old Justin Bieber and Black Eyed Peas' will.i.am sent Brit tweets to say happy birthday, and while she has yet to thank them, we're sure she feels extra appreciated today. Also in today's best tweets, Nicki Minaj saw some celebration of her own on the heels of her new song release, 'Roman in Moscow,’ while Shakira promoted a new video from her live concert DVD. Also, Victoria Justice teased a potential new role and Tinie Tempah left us all wondering which "big rapper" his forthcoming new track will feature. See what your favorite pop stars were tweeting about today!