For some reason i have a lot of different save games files, so i decided to make 1 big combination of all files with MCEdit... But i got 1 problem.. In most of the maps i've ran far away from the first spawn point, so how do i find the places i've built houses and stuff?
Zoom out, a lot.
You should now see a grid display. There should be an outline that separates explored land from unexplored land. I think explored areas are highlighted as well. Find the general area/direction your castle was in, and fly that way. I used this when I accidentally popped out of the Nether a long way away from my home base.