By default MacBooks save the contents of memory to disk every time you suspend (close the screen). I have 4 gigabytes of RAM and often run many apps at once and this adds a few seconds each time I open or close the screen. Much more irritatingly, sometimes this step doesn’t work and I have to restart. Grrr!
You can set the default behavior to not write to disk but then if you laptop is low on battery you can lose your work. More grrr!
SmartSleep by Patrick Stein is a neat solution that changes the mode to RAM only until the battery falls to a particular level when it cuts over to RAM+disk. Highly recommended and free.
Patrick is also the author of another favorite utility of mine, Screen Recycler. If you have an old Mac or MacBook you can use Screen Recycler to add a third or fourth screen using VNC.