An excellent place to get some great sustained Mandarin listening practice in is right in the comfort of your own easy chair while watching a Chinese movie or TV show. There's been a recent upswing in Chinese video production and there are a multitude of movies and shows to choose from. If you're not quite ready to jump into a Chinese show, there are also many American movies and shows that have been dubbed in Mandarin.
Be reminded that you won't just jump into a historical kung fu flick and understand everything. If you're a beginning learner, I'd suggest checking out a cartoon like Spongebob Squarepants or a sitcom like iPartment. These shows and more can be found at www.youku.com and elsewhere on the web.
If you are a foreigner living in China, an added bonus of watching movies and TV is that it becomes a perfect conversation starter and topic for you to practice your Mandarin with your friends. You can also choose to learn Chinese online, Hanbrige provides different Chinese courses online, and no doubt that Hanbridge Chinese online teaching is excellent with the most professional teacher and advanced online teaching system. Everybody is always ready to talk about their favorite characters, plot twists and cliffhangers. So pop some popcorn, pull up a chair and start learning Chinese!