Companion plantings

I've researched companion plantings for a while now; the subject is fraught with contradiction and variation, so I guess you just have to see what works in your garden. There's a lot of advice, for example, about planting marigolds. But the slugs love mine so much they've devastated most of the flat I planted this year, on their way to the seedlings.

The book to have seems to be Carrots Love Tomatoes: Secrets of Companion Planting for Successful Gardening, which is useful and interesting and arranged encyclopedia-style. A few others appear in the bibliography of this 3 page fact sheet from the Toronto Botanical Garden.

Here are some websites and tables to consult as well (I have also tried to work out where these sites are located as this is of course critical to growing anything-- the librarian in me is having hissy-fits over how many gardening sites don't seem to think it matters if people know what climactic region they're based in):

About.com - Companion Planting - article geared towards organic landscaping, but with a lot of useful links at the end.
Basic Info 4 Organic Fertilizers - Companion plants to ward off pests - alphabetical listing (Texas)
Cass County Extension (from North Dakota State University) - Companion planting - table listing most common vegetables, their friends and enemies. (North Dakota)
Gardens Ablaze - Companion planting for better yields - detailed table listing plants with compatible and incompatible companions [California][?]
Georgia Strait Alliance - Alternatives to Pesticides - pdf file with lists of plants that will attract beneficial insects and repel or deter pests, and suggestions for a number of alternative treatments to problems like fleas and powdery mildew, and notes about insecticides Pyrethrum, Pyrethrins and Rotenone. (Nanaimo BC)
HowToGardenAdvice - Companion Planting for your Vegetable Garden - some useful background and a table with links to growing tips for different vegetables. [Arizona][?]
Tinkers Gardens - Vegetable companion planting chart - two tables, for vegetables and herbs, with good and bad companions. [Texas][?]