Robert Jordan's the wheel of time series (rereading it, one of the best series ever written and hailed as the next lord of the rings)(one of the few novels i know that has spawned not only a video game, but a soundtrack and a tv series that never got made)
George R. Martains's A song of Ice and Fire series. (great recommendation)
the first book is called A Game of Thrones. I think this guy is a better writer than tolkein to be honest, and I wont be suprised that 20 years down the line if they do not threat this series in the same light. This guy really is the best writer I can think of, and I have read a lot, even the classics.
The Drangon Lance and Forgotten Realms collection of Dungeons and Dragons books is also fairly good. The famous writer R.A Salvatore wrote a number of books, a big series in fact, for forgotten realms. You might have heard of the hero he created, Drizzt Do'Urden. That fictional character has more fansites and press than any i have ever known from a book series.
Ann Rice has a series about Vampires. Also very good, very strange though as well. Her books spawned the movie Interview with a vampire, later queen of the damned (horrible movie but the book was good), and some other things.
ok thats just a few. Those series alone have a large number of books and would keep anyone busy for a long time.