Wireless range extension

Is there a way to extend my wireless range without buying a new antenna? 

I'm running a notebook with a built into the montor antenna.  The wireless card is by Intel and after looking around briefly I have changed to netstumbler as my prefered wireless software (for now).

I remember seeing wireless extenders, which were separate antennae that you could place around the house to extend the range. They also have outdoor-safe versions. I know it's not what you asked for, but there isn't much you can do otherwise, I think.