Here are some links to companion planting information.
Companion Planting– This page from ghorganics.com is an in-depth guide.
Companion Planting Charts for Vegetable, Herb, Fruit and Flower Gardening – Chart format of companion and incompatible plants
Here’s a link to quick view in Google of a pdf excerpted from Companion Planting, a book from Rodale’s Successful Organic Gardening series. Once it opens you can download the file form the File menu.