Yeah, Airdrop is the Apple version of #2 on my list. It's particularly neat if you're in a situation where you want to exchange files with someone, but aren't on a common network.
If you're on the same network, it's just about as simple as Prefs >> Internet/Network >> Sharing, enable file sharing! You'll want to read a few more of the fine details (and that link above is excellent too).
I don't use many widgets, I'll hop over for the calc, or to check out iStat (a machine status/heat/fans monitoring widget, very nice).
On the same network, you can also share/use other services like iTunes Home Sharing (accessing the same iTunes library across devices), peer based iChat (vs. routing through an external chat relay service), etc.
You can also share files across a Windows network, which is great way to setup a cheap server if you want a centralized file sharing machine.