Digimon Adventure: Our War Game
A year after the events of the first season, a virus Digimon called Diaboromon appears and starts attacking the Internet. The children and their Digimon unite once more in order to prevent him from destroying every communications network on the planet.
Managed to see an English subtited version of this, mush better than the hacked up and mismatched American version.
Really neat -- I love how the internet is represented as a physical space in this one. You can really see how it paved the way for Mamoru Hosoda's later film "Summer Wars," which expounds on a lot of ideas laid down here.