From Real Movie News:

With an extra 8 minutes worth of footage, the new version of ‘Spider-Man 2.1’ adds even more to what is already a classic of the genre.

The extra footage is mainly to do with character development and is mainly there to set up storylines that will be explored in the third movie. There is more interaction and conversation between Harry Osborn and Peter Parker, over the death of his father and what Peter would do if he could get his hands on the man who killed Uncle Ben. There is also more interaction with Peter and Mary Jane. The largest percentage of the extra footage is the extension of the main fight scenes between Spider-Man and Doc Ock. Now we see more of the fight after the bank robbery and the battle on top of the train, which only adds to the excitement.

‘Spider-Man 2’ was already an outstanding movie but these extra minutes just make it even better.

Spider-Man 2.1 Widescreen Extended Cut