Jonn,
Sometimes this varies by City & State. Ya gotta check with your area.
Faron

This does vary from code to code, but 2' max. seems to be common among a lot of them.

Riles

Rule of thumb for cantilevered decks, whatever hangs over must have twice as much before the other way. By that rule you could go 3', but I'd stick with 2' as the max.

Al

The 2002 IRC building code says the following:

9. Floor joists for exterior decks may be cantilevered a maximum of 24" with the following conditions:

a. 2X10 SYP joists, 16" on center
b. 2" nominal or less wood plank floor.
c. No stair stringers of platforms supported by cantilever.
d. Toe nail bottom of joist @ support girder.
e. Framing is to be right angles to cantilever support girder.
f. No roof load on cantilevered floor section.

So if your local jurisdiction uses the IRC they will probably require that you use 2X10 joists or you could always have a structural engineer approve your plans which they typically accept.