This one :) I'd be glad to help. As far as online resources go... well, I suppose http://www.serbianschool.com/ has a couple of interesting things, although it's by no means a good website.

www.busuu.com and www.livemocha.com :) I use them for Spanish, and I think they're really good :) you can learn any language on them :)

www.livemocha.com lang-8.com www.busuu.com Срећно!

http://www.bbc.co.uk/languages/other/quickfix/serbian.shtml

http://fsi-language-courses.org/Content.php?page=Serbo-Croatian