Luna already has the 15" Titanium PowerBook so I can just use her's for free.
I've also thought of just getting myself the 15" iBook since it is so cheap and almost indestructible, but since it is only a G3 processor it really isn't good for anything but surfing and watching movies, but you can throw it in a backpack and even drop it without it breaking since it is designed for school kids. It also has other limitations like no PC slot and unlike the PowerBook it doesn't support using a 22" monitor as a second display, I really like working with two displays.
I could sell my desktop setup to one of the designers that I work with and that would be half the money for the 17" Powerbook, but I'm not sure if I would be happy with only a laptop. You can plug in a 22" monitor right into the Powerbook and have a two monitor setup just like how I use my desktop machine now and would be about the same speed as well.
Then again I could just do nothing and share Luna's PowerBook…