You can split windows in vim and keep multiple files open. This isn't usually that interesting to me because I use screen for everything and memory usage isn't really an issue.
What *is* useful is that you can have two views into the same file -- so if you want to reference something way up top but you're working way down at the bottom, you can split your view. Here's how:
:sp (splits window)
CTRL-W up (move up)
CTRL-W down (move down)
:q (closes this window)
You can find a lot more info and additional commands if you search for "vim split window" or somesuch.
Pretty rad!
