There's an A and a B list - the veg on each are all listed in the "So you're thinking of doing Atkins" thread. I keep forgetting which is which, so picked out the veg I like and have stuck a list of them on the fridge.
I usually do a cup of green leafy stuff, and a cup of cucumber/mushroom combo, so I can then have a cup of tomatoes, which is on the B list because of its higher carb content.
Much easier to go by cups when making up a salad at top speed in the morning