changing partition sizes?

[Moss Collum]

When I first partitioned my hard drive, I seem to have underestimated the
amount of space I'd need in /usr.  Does anyone know of a safe way to
change the size of a partition after it's been created?

Alternately, my /var partition would be happy with less space, and is as
large as I need /usr to be... would it work to switch them with each
other?

(I'm thinking something like this: move everything from /usr and
everything from /var into subdirectories under /home, unmount them, switch
them, and move everything back... but this seems like it might be a bit
risky. Anyone?)

--Moss Collum