Yes, finally the Grand Theft Auto Website is up, and really makes you want to wait for the game more and more! Showcasing the Liberty City view, and then giving sneak views of the different places, characters and locations that will be featured in the game.
GTA4 to include Multiplayer:
Also in the website, is a litle button “Multiplayer” which says Coming Soon on mouse rollover, which only means that GTA4 will have a Multiplayer mode to please the masses 
Official GTA4 Theme:
The website gives a litte description of the theme of the new installment on its Introduction page, which is given below:
“What does the American Dream mean today?
For Niko Bellic, fresh off the boat from Europe, it is the hope he can escape his past.
For his cousin, Roman, it is the vision that together they can find fortune in Liberty City, gateway to the land of opportunity.
As they slip into debt and are dragged into a criminal underworld by a series of shysters, thieves and sociopaths, they discover that the reality is very different from the dream in a city that worships money and status, and is heaven for those who have them and a living nightmare for those who dont.”
Stuff to Download:
Also up for the grabs are Videos (which are splendid!), Official Wallpapers, Screensavers, Avatars, and Buddy icons in the downloads section.
And here is the official game cover, on the lines of Gta: Vice City.
Developed by Rockstar North, Grand Theft Auto IV will be simultaneously available for Xbox 360® video game and entertainment system and PLAYSTATION®3 computer entertainment system and will be in stores worldwide on April 29, 2008.
[...] the GTA 4, will take around 100hours to complete. Grand Theft Auto 4, Liberty city, who’s Official Website was announced only recently, is one of the most anticipated games of the Year 2008, with a lot of [...]