Target Disk Mode to boot from MacBook

If you want to put your MacBook (with Leopard) into FireWire Target Disk Mode and use it's hard drive to boot the iMac, that should be doable. I have a small external FireWire drive with Leopard that I use as an Emergency/Maintenance Startup Disk for a few Macs, PowerPC and Intel. What you propose would not be any different.

If the MacBook is a newer model that came with Leopard, I would not try it the other way, using the iMac (with Tiger) as the target for the MacBook to boot from, because the MacBook may only support booting Leopard (or later).

There's also this clever program that uses VNC to let you turn the iMac's screen into a second screen for your MacBook. Or the other way around...

http://www.screenrecycler.com/home.html

I use it along with an old laptop running Ubuntu Linux, to give my iMac a THIRD screen.

The resolution can be whatever you want it to be (just change it in System Preferences Displays pane). The refresh rate is a bit slow because it's going over the network. It work much better if you use an Ethernet cable at gigabit speed, versus Airport.

I have my third (ScreenRecycler) screen showing mostly static windows, such as my email list in Mail.app and Address Book.