There is an app online that I tried last year that might help you out. I'm pretty sure it was the one at smartgardener.com. (For a visual:
http://www.smartgardener.com/g... ) Ultimately, I wanted something that allowed for more aesthetic design in my garden, but the app will give you a very practical and useful layout if your chief concern is production and simplicity.
Another idea, along the lines of what you mentioned with Excel, is to create your own. Last year I used OpenOffice Draw (Open Office is like Microsoft Office, but open source/free) to create my own garden map that looked like this:
Here is a close-up:
This is the final copy of what I planted (far too late, if you notice the dates) last year. My previous plans had a lot of hand-written notes and adjustments to the layout. I did my other raised garden beds in a similar fashion, but they are on a different page.
Edited to add: to create my garden bed layout, I also used the information on companion planting at Wikipedia, as well as 1-2 other companion planting websites. That Wikipedia companion planting guide is SO handy, though!
