In The Hobbit, the One Ring turned Bilbo invisible (more or less completely) along with his clothing, armour, etc. However, one passage in chapter 8 suggests that this power did not extend to his sword, Sting:
With that he [ring-wearing Bilbo] turned and found that the last space between two tall trees had been closed with a web—but luckily not a proper web, only great strands of double-thick spider-rope run hastily backwards and forwards from trunk to trunk. Out came his little sword. He slashed the threads to pieces and went off singing.
The spiders saw the sword, though I don’t suppose they knew what it was, and at once the whole lot of them came hurrying after the hobbit along the ground and the branches, hairy legs waving, nippers and spinners snapping, eyes popping, full of froth and rage.
So it seems that the ring's power to make invisible was not as effective as expected. Can somebody explain this? Would the fact that the sword was Elvish have any bearing on this?
In the next chapter, Bilbo steals keys from the Wood Elves (and later, food the Raft Elves). This led me to imagine that the keys might have been floating in mid-air as he carried them around the palace.