Paparazzi flashbulbs nearly outshone the ubiquitous neon signs of Las Vegas when chart-topping artists from Destiny's Child to the Dixie Chicks descended upon the MGM Grand hotel to get honored - and then get down - at the 2000 Billboard Music Awards.  "Just looking at the lights in the town puts you in a good mood," chirped Britney Spears, who sported a showgirl-ish feathered fedora.  "I'm ready to party!"  Following the Fox-broadcast ceremony, she and her 'NSync boyfriend, Justin Timberlake, did just that, swinging by big winner Sisqo's celebration inside Jack's Velvet Lounge at the Venetian hotel.  The jubilant "Thong Song" singer - whose Siegfried & Roy-like party featured a full-grown tiger and a barefoot fire-eater - enthused, "I just won six awards!  For somebody who always has something to say about everything, man, I'm suddenly speechless."  More talkative were the members of 'NSync, who took devilish delight in teasing ersatz high roller Joey Fatone over his empty pockets.  "He's a big gambler.  He's just not a big winner," joked Lance Bass.  "Yeah, put it this way," added Timberlake: "He lost enough money to buy this whole hotel."