Generally Crime and Punishment is Dostoyevsky's most influential book. Also recommended are his short stories, which was more his forte. The Idiot and Notes From the Underground (if you are interested in historical context, especially). The interesting thing to keep in mind when reading Dostoyevsky is that his political views changed over time, from being in line with the intelligencia of the time (the forerunners of teh Bolsheviks) to having a kind of spiritual re-awakening, and becoming rather Christian later on (though he keeps it under control, thankfully) In some of his writing he implies that Marxism can't work because it's too materialistic.

Interesting linguistic side note: the more accurate spelling of 'Leo Tolstoy' is apparently 'Lev Tolstoi', according to [caught you ego-surfing. google-proofed your name]. She learned Russian in school (yay communism) and says that the 'v' and 'w' are interchangeable, so Lev is pronounced 'Lew', which got changed to 'Leo'.

For Tolstoi my two favourites were War and Peace and Anna Karenina (sp). Both long, but very self-explanitory, and thankfully free of literary reference one-upmanship that made English writing of the time so irritating for me to read. (though that could just be because of translators ironing over such allusions)

Other Russian authors to look out for are Chekov (mostly short stories) and Pushkin (poetry). And moving into more modern work, anything by Alexander Solzhenitsyn is quite good, as well Dr. Zhivago by Boris Pasternak is worth reading for a personal perspective on life under Lenin, and seeing the creaky underbelly of the revolution.