Rogue or Sorceror
I voted rogue, but for me it was a toss-up between that and sorceror.
Rogue's have many skills, so the new player can always feel like he/she is contributing. They have few special abilities and/or feats which mean fewer things to worry about.
Sorcerors have such limited spell selection, that with a little DM help, the newbie can be up and running around as a magic missle, sleep, or colour spray machine.
One of the main advantages to both classes for newbies is the fact that many typical attacks by these two classes are ranged attacks. This means that a newbie won't usually have to worry about AoO, flanking, strategic placing, etc. By restricting the "wargaming" aspects of 3e, they have more time to learn the basics.
I don't think fighters are as appropriate for a newbie as they were in previous editions. Quickly the options that become available through feats may become overwhelming to newbies.
Acmite