Hello all the good slavic people of the world!
I thought this might interest you. Some clever guy developed a langauge which all slavic people can understand (more or less) without any learning whatsoever. It's called SLOVIO (after the word slovo I guess) The only requirement is to know at least one slavic language. So it's kinda like a Slavic Esperanto except that you don't have to learn anything to get the basics down. I tried it and I must say it works well with Slovene - I pretty much understood the majority. So it goes well with the South Slavic group (my guess is Serbians, Croatians and possibly even Bulgarians shouldn't have many problems then), now I want all you Russian, Czech, Slovak, Polish, speakers to try it out and see how it works with the East and the West slavic languages.
This is the official page
Some more facts about the language:
Slovio language
Slovio is a written and spoken constructed language created by scientist and linguist Mark Hucko. Slovio is an international help-language created to help Slavic speakers intercommunicate. The grammar of Slovio is similar to Esperanto, but the vocabulary is derived from the most common words from Slavic languages. According to Hucko, Slovio is understandable by more than 400 million people throughout the world without any prior study of the language. The name, Slovio, comes from the pre-Slavic word "slovo" which means "word."
As of October 2003, the vocabulary of Slovio contains about 12000 words.