It is possible as long as both laptops are on the same network (which should be the case for most home users and offices. I never tried it out for myself though. There are two option that I know of:
Maxivista software for $40, but there is a trial version.
http
/www.maxivista.com/
ZoneOS ZoneScreen is free, but you probably have fumble around to get it working.
http/www.zoneos.com/zonescreen.htm
EDIT::
Looks like Maxivista was already recommended when I stepped away...