"Saber" is used when you have something related with the knowledgment (academic subjects) or the ability to do something (as "learn"). For example: I want to know Analytic Geometry. Eu quero saber Geometria Analítica. I want to know (learn) how to cook this dish. Eu quero saber preparar este prato. I want to know (learn) how to play the piano. Eu quero saber tocar piano. "Conhecer" is used in practice of something or when you want to "meet" something, somebody or someplace (not academic). For example: I want to meet your friend. Eu quero conhecer seu amigo. I want to meet Russia. Eu quero conhecer a Rússia.

Alexandre says interesting things here, with which I support... and won't 're-say' ... I would just add that in Portugal (I'm from Brazil, alright) and in Latim (Medieval culture), the term "saber" has relation to "taste" something. When "conhecer" has an intelectual inclination (academic, in Alexandre's words), saber has a sensorial (sense) signification. So, in Portugal, one may hear, not often I must say, "Eu sei o gosto a que estás a referir" (literaly: I know the taste you are referring to). That's it! Have good answer, I hope!

O conhecimento é objetivo, transmissível de forma indireta ou impessoal, podendo ser adquirido através de livros, computadores, enquanto o saber só é transmissível de modo direto , de pessoa a pessoa , sem possibilidade de sistematização . Ou seja: saber é intelectual, conhecer é prático. Knowledge(conhecimento) is objective, transmitted indirectly or impersonal, which may be acquired through books, computers, while knowing (saber) it can only be transferred in a direct, person to person, without the possibility of systematization. In other words: knowledge(saber) is intellectual, knowledge(conhecimento) is practical. Obs: Sorry if English is imperfect, but I'm still learning. I used dictionaries to write this.