Your main problem here is the number of projectors to choose from.
They all have a VGA (Video) connection and cable and all you would need for the MacBook is the mini DVI to VGA adapter which is available from the Apple store.
No special software is required to make the projector show the picture, it basically just shows what is on the screen on the laptop.
The MacBook would probably be the better choice as it is a lot more portable.
Now that you have a method of projecting the movie, how about sound?
My husband really wants to be able to watch movies outside this summer. We have MacBook and a G5 (both 2007 models).
I think I need to buy a projector to be able to project DVDs on to the wall outside, but have no clue what type of projector or what cables would be necessary. (Distances is about 15-20 feet) Also, if software is necessary? Any tips? Want to take care of this for Father's Day... but can't ask questions without giving away my motives. Thanks.