It's a minor failing of 3E that it doesn't allow for spear & shield. The phallanx was strictly a military formation, and the hoplite's panoply was not the best kit for a duel, so it's an understandible omission.
In 3.0, you could 'fake it' using a Tower Shield and (of all things) a Heavy Lance. This gave you stabby weapon with reach, and a shield defense with facing, both of which you really need to capture the feel of the phalanx - the advancing wall of spears and shields. It'd also be realistically ineffective in many D&D combats.
In 3.5, you have to stretch even further, arming yourself with a 'small' (for a small-size character) reach weapon, and a Tower Shield. This gives you a -2 attack for the wrong-size weapon, and another -2 for the Tower Shield, making it quite a poor choice of armament - even the advantages of formation fighting probably won't make up for it. Oppossed forces of 1st level warriors so armed would hit eachother only on a 20.
I like the idea of ruling that simple two-handed spears (which includes the Longspear in 3.5) can be used one-handed with Martial Weapon Proficiency. It enables a much more straightforward modeling of commonplace historical tactics, like the phallanx.