True, it is also good to have an idea which tone means what. As far as I know it's: high-level, raising, falling-and-then-raising and falling (the shape of the dashes over i gives the hint) http://en.wikipedia.org/wiki/Mandarin_phonology#Tones
http://www.mdbg.net/chindict/rsc/audio/voice_pinyin_cl/shi2.... (shí)
http://www.mdbg.net/chindict/rsc/audio/voice_pinyin_cl/shi3.... (shǐ)
http://www.mdbg.net/chindict/rsc/audio/voice_pinyin_cl/shi4.... (shì)
For the falling-then-raising (shǐ) changing the "shi3" to "chi3" in the URL gives a better idea, I think, for what the inflection sounds like.