Pronounced like the "r" in "run", but it is rolled. (Equivalent to the english letter "r"). Searching "Russian rolled r" on google or youtube will show you many examples.

I made the record, but the quality is bad. Sorry for that. Russian words sound clearly and try to listen, maybe it wll be helpfull a little. http://vocaroo.com/i/s04WX4nVeXst On this site you can listen all Russian letters - http://masterrussian.com/russian_alphabet.shtml