Spider-Man 2 grossed $40.5 million in over 4,000 theaters on Wednesday, breaking the previous record for the biggest Wednesday ever set by Lord of the Rings: Return of the King ($34.5 million). It also beat the opening day for Spider-Man, a $39.4 million Friday. It may or may not have been the biggest opening day ever, since the opening day of The Matrix Reloaded started at 10 p.m. the previous night (and brought in $42.5 million in the 26 hour period).
The biggest six day opening ever was The Matrix Reloaded, with $152 million for the period.