TaoTeChing

LaoTzu's classic. Various good translations are available. I quite like RedPine's one.

TheArtOfWar

SunTzu's classic on strategy. Still looked at by modern students of military strategy. ThomasCleary does a good translation, LionelGiles did amongst the earliest, and his version is public domain.

TheTaiChiClassics

LoAnnImackerFoe is the most common translation of these short treatises on what the ideal of TaiChiChuan is.