Nifty symlink cheatsheet
$ln -s TARGET LINKNAME
In the Mac OS world, symlinks are called aliases; in Microsoft Windows, shortcuts have a similar function, but work slightly differently: they're simply text files containing the location of the target. Whether they should properly be called symbolic links is probably debatable.
Regardless of your OS of choice, symlinks can save you loads of time finding stuff, and are also very handy to give to users to keep them from nosing around your filesystems.
Some info contributed by Shadownode and JerboaKolinowski