My house rules list three categories of books (and there is a fourth category assumed). I list primary, secondary and tertiary sources. Things from primary sources can be assumed to be allowed, unless I've specifically stated otherwise. Things from secondary sources will probably be allowed. Tertiary sources are other books I own and I will consider allowing something from those books. I don't list an other category, but it's similar to tertiary with a lower chance of being allowed (since I don't have them).
Players are expected to ask my permission to add anything from a non-core book (which, for my campaign, are the 3 core books, the Eberron campaign setting and the Expanded Psionics Handbook). I read my email several times a day (and check my forums), so getting an answer typically pretty quick.