If the laptop has a functioning OS, you just need to make or buy a Cat5/6 network "crossover" cable and do a bit of configuring so that they can talk to eachother without a switch/hub. I need to set this up myself so I'll try to remember to author and share a howto when I do.
You can get simple access to the shell through ssh this way. if you want a graphical environment you are going to need to do some more leg work, TightVNC, as you mention, is one option. X11 forwarding is another, but these won't be very enjoyable for media-rich graphics activity.
if you also need internet access, at least one of the two machines will need a second network adapter in one or the other (wireless, wired, or 3g dongle).
if your goal revolves around portability but you need graphics performance too, take a look at the lapdock raspi projects:
http://www.adafruit.com/blog/2012/06/21 ... a-lapdock/
http://www.raspberrypi.org/phpBB3/viewt ... it=lapdock