So I've managed to survive the onslaught of Tallbirds and get a few Tallbird eggs. How do I hatch them? And what are they useful for (other than pecking you to death when they grow up)?
To quote the Don't Starve wikia,
A Tallbird Egg can also be placed near a fire, where it will become a Hatching Tallbird Egg and eventually hatch into a Smallbird.
A Hatching Tallbird Egg is a Tallbird Egg that has started to hatch after being placed near a Campfire or Fire Pit for at least 10 seconds. Hatching takes roughly 3 days before it will become a Smallbird.
And concerning the second part of your enquiry, a similar question has already been answered on the stackexchange.