I'm studying Mandarin through software... I'd say I'm at an advantage because I already speak Vietnamese, so I've got experience with tonal languages...
There are four tones in Mandarin, and I believe the best way to learn them will be through this short video:
http://www.youtube.com/watch?v=q8Ll7qTOmx0There are many such videos on YouTube.
chinese-tools.com is also a great help.