Risus Monkey made some good points, some of which I would also have noted, others I wouldn't - not that they aren't noteworthy, but I simply wouldn't have thought of them. Anyway, those notes that I would have added are:
Bilbo's ability to enrage the spiders by singing rude songs about them is likely an inspiration for the Bard class.
There may have been some inspiration for the Web spell in this chapter, though it's rather iffy there.
I thought this was a trade route at one point? Why is a small boat across a very dangerous river the only way through?
Why is it that they don't fall asleep when trying to wake up Bombur? No mention is made of giving him time to dry off before doing so, which means that they should have gotten the magic water on their hands.