A comment I submitted to one of PETA's info pages, here;
As a vegan working in McDonalds, I sometimes find myself having to take advantage of the free lunch offered each shift.
(In Britain) the fries are vegan. All of the soft drinks are, except the fanta, which contains gelatin (smarties are also not vegetarian or vegan, and nor is the sour cream and chive dip). A hamburger with no meat is vegan (although some ingredients are made in a factory containing milk, and it can't be guaranteed that it contains no dairy products at all). An M burger with no meat, cheese, or sauces is also vegan (it's a lettuce and tomato sandwich). Generally speaking, the buns alone are vegan, so you may be able to build an option, depending on how helpful the staff are.
A veggie burger, at McDonalds, is not vegetarian unless you specifically request that it is cooked in the fry vat. Otherwise, they can't guarantee that it won't come into contact with the oil from the chicken or fish (same applies to the apple pies, but I suspect they contain egg too - I'd have to check). A veggie burger cooked in the fry vat with no sauce is vegan. A veggie deli without the mayonnaise is also vegan (remember the fry vat).
A garden side salad with balsamic dressing is vegan, but none of the other salad options are.
On the breakfast menu, bagels, hash browns, oatmeal, jam, and golden syrup are vegan.
Edit; Sorry, the oatmeal isn't vegan, but the apple pies are if they're cooked in the fry vat, or if you don't mind the risk of their coming into contact with the chicken or fish oil.