I don't know if this is the best way to put it. But, when I think about single-edged (curved or straight) swords and daggers weapons were the majority in the eastern part of the world and double-edged (straight) swords and daggers where the majority in the western part of the world.

Is this true to some extent?

I was also curious if someone could show me some pictures of single-edged daggers from antwhere in the world, because I'm having a hard time trying to find some? :)

Well, saexes are defenately single edged, and western

Scottish dirks are often single-edged, and single-edged backswords were also popular amongst the Scots.

It depends. Different times, different swords just about every place.

I think as a general rule, you should NEVER generalize....oops!

I thought that the seax was more of a large fighting knife than a dagger.

problem is that it is not so easy to make out what the difference is between a dagger and a knife, or it is hard defined (as a double edged knife with a guard and an acute point) so as to rule out later combat knives, but then there will be no single edged daggers. The dirks with single edges slipped my mind, they were a better example, a knife with a guard and an acute point.
There are many instances of single edged swords used in western europe, from falcata to sabre, there was always some form of single edged sword in use (as far as I know). As for eastern, there are quite a few examples of double edged swords there too.

If you check out our Features on the Rondel Dagger and Scottish Dirk, you'll see a number of examples of single-edged daggers. Many dirks were made from cut-down backsword blades.

A quick search on saif, "Arab swords," "Mamluk swords," or the Chinese jian, whether on this forum or in the Web at large, will provide you with many examples of straight, double-edged Eastern swords.