I've had a look around and found a good IGN article on it which identifies 3 swords.
Glamdring, The Lord of The Rings
Robin of Loxley's blade, Robin Hood
Kingdom of Heaven blade
Elio also mentions on reddit that he noticed a lot of other Kingdom of Heaven blades in the throne but I can't see any identifiable ones in there.
Having visited the set during the first season filming, I got a very close look at a protoype of the Throne in a half-completed state that was in their prop room, and I believe you are exactly right that they collected weapon molds from all sorts of sources.
I specifically recall that several of the swords had marks indicating that they had originated from Ridley Scott's Kingdom of Heaven.
The above comment by Elio might not be 100% accurate as westerosorg has started a new series called "Westeros.org visits... Northern Ireland Game of Thrones territory". Entry #3 in this has the following information so it isn't entirely clear if these swords made it into the final Iron Throne or just the prototype Elio saw.
Set Visit entry #3: A piece of an Iron Throne prototype, stored in Props. As I've mentioned before, I got quite a close look at this, and noticed some of them were stamped with "PROPERTY OF KINGDOM OF HEAVEN", meaning they used props from the Ridley Scott film. Rumor has it that Lord of the Rings prop swords also ended up in the throne... #GameOfThrones