I'm a "iconic concept" sort of guy when it comes to class design. Every class should express a core, iconic concept clearly and as simply as possible, and without infringing on other classes except by design.
At the moment, I've come up with four martial/warrior classes, with the potential for at least three more. They all share the same save progression, to-hit chart, and hit points (yes, even the barbarian), but they do different things.
The fighter is the most generic. She gets a weapon mastery bonus that slowly progresses as the character levels up; this bonus can be applied to one, two, or three weapon groups. Concentrating on one weapon gives the highest bonus. She also has strong defensive ability that can be used in place of an attack, and finally gains a second attack per round. Fighters can also apply their Strength bonus to their to-hit chance, currently the only class that can do so.
Barbarians don't gain weapon mastery, but they do rage. This gives a bonus equal or better than the fighter's, but has a limited duration and some potentially serious penalties as well. Barbarians are also the best at slaughtering massed hordes of weaker creatures, with cleave and whirlwind of steel abilities.
Rangers are the implacable foe, and gain a bonus versus certain types of opponents. The bonus and number of opponents increases at 5th and 9th level, both to reflect the ranger's increasing expertise and the likelihood of encountering certain creature types. This bonus applies not only to attacks and damage, but saves and checks as well. The creature types can easily be changed in different campaigns: evil or outlaw humans, monstrous humanoids, monstrous creatures, spellcasters, etc.
Paladins are the divine opponents of supernatural evil, and hew reasonably close to what's been done before.
Knights, soldiers, and swashbucklers aren't fully defined at the moment, but the concepts are visible. If barbarians are the masters of brute combat, knights are the elite one-on-fighters of the battlefields, duking it out with the big bad boss monster. Soldiers are tough, adaptable survivors - sturdy and reliable. Swashbucklers emphasize dexterity and movement over force and stamina - the chief problem with this class is that it could be very similar to the fighter in execution.