I would like to setup a fileserver, accessible by my friends with a minimum of effort (ideally, just type in something on their browser's location bar and see a list of files/directories), and... I have not the least idea where to start.
Ideally, I'd be able to control who can view what - i.e., I could set a directory, restricted by password or IP or whatever, to be in no way accessible to anyone other than my brother.

Note that I well understand that I possibly have no idea what I'm talking about here.

Get a free domain and server from x10hosting, then set up a small site that basically just has a password system in PHP, then once you enter it you can see the links to all the files.

this is a better free hosting site

Yeah, but xxx.ExoFire.net looks cool

Thanks for the links, but...
The stuff I have for sharing totals over 30gb, and I have no idea how much or little of it actually will end up being taken. Thus, I need a method to distribute it from my own computer.

If your brother and you are connected on a network together, just share the folder that has the things you'd like to share with him..

Get a mini portable harddrive

Which doesn't help me distribute files to people who aren't in my LAN.
I have one.
I'm not mailing it to my friend who lives about twelve states away. Nor the one who lives five. Nor the one who lives...
...

I use XAMPP... You could get the lite version which isn't as fancy. I use it partly to share files and partly to test PHP stuff locally. You can run or stop apache whenever, and it is really easy to set up.
I don't know if this is more than you are looking for.