A different take on the time travel plot. In the Year 2148 the lone surviver of the human race makes a gamble to save humanity, using the note left behind by his lost love he sends a messenger through time to the end of 20th Century. Whether or not time changed for the better is yet to be determined, what is important is that the Light now has a fighting chance.
GraysonPaladin here, I haven't done any Naruto stories yet. Current stats: 1 Galactica/Honor Harrington cross, 1 Honor Harrington/Bleach cross, 1 Ranma/Negima cross, 1 Avatar: Last Airbender, 1 AtLA/Sailor Moon cross, and 4 for Sailor Moon.
Currently when I have time I'm trying to rewrite my Galactica/Honorverse story.
I do have a bit of a weakness for Harry Potter crossovers >_> (don't read HP fanfiction on its own, but with Naruto... or, well, Hitsugaya on occasion...it's fun) With Naruto, it usually goes with the shinobi lands being a sort of hidden continent, which with all the magic etc floating round is just about workable - and as far as Bleach goes, that's easy. There are very few decently written ones though. Mostly they're terrible for one reason or another - but once in a while, it works :3
Or are Yoai... I like HP/Naruto crossovers as well but so many of them are Yoai or Slash, or are Konoha or Sakura bashers.