Just a quick note: These sorts of questions should probably go into the
Sandbox Forum under the Sub-Forum
Player's Help. (just a friendly FYI, I moved the thread to the appropriate forum

)
Sure:
Two weapon fighting gives you an extra attack at your full BAB with the appropriate penalties for the types of weapons used on all attacks made in the round.
This is why the improved two weapon fighting feat states that the extra attack made with it is at a -5 penalty, and the greater states that it is at a -10.
So with Two weapon fighting at 6 level fighter and one light weapon (primary weapon doesn't matter -- you could use a one handed and light or two light weapons with the same penalties):
+4 (primary hand) +4 (off hand) -1 (primary hand)
With two one handed weapons it would be:
+2 (primary hand) +2 (off hand) -3 (primary hand)
With improved two weapon fighting at 6th level fighter with one light weapon (again the primary weapon doesn't change the penalty only the type of the secondary weapon) you would have:
+4 (primary) +4 (secondary) -1 (primary) -1 (secondary)
With two one handed weapons it would be:
+2 (primary hand) +2 (off hand) -3 (primary hand) -3 (off hand)
This is easily confirmed by looking at any NPC stat block produced by WoTC for the 3.5 system.
Don't dance a bear in a torilla suit in front of a room full of oranges if you don't have the monkeys to catch the surf afterwards.