1) A language translation application
> All I know of is Kbabel. Never used it, but i've heard its good.
http://i18n.kde.org/tools/kbabel/
2) A world time zone conversion application
> kworldclock does the job for me.
3) Some sort of map application for travel, with some sort of map database
> I usually use the maps on google. Here is a link I found:
http://fmaps.sourceforge.net/
Are you like, going on a vacation or something