Frommer's and Fodor's (what is it with F and major brands of travel guidebooks) both have significant lines of With Family/With Kids/With Children. There's also a Kids Go! line of maps and guidebooks. Lonely Planet has a with kids book (ordered it, despite middle starred average review because it suffers from the classic U shaped review distribution of a book which does not match its obvious audience) and there are a handful of books about getting outdoors (one has a mountainbike with a trail-a-bike attached -- biking through a meadow! Bought that one) and exotic destinations with kids. As near as I can tell, we can expect Time Out!, Let's Go! and Michelin to never, ever, ever issue guidebooks focused on the kiddies, given their audiences.
In the course of ascertaining the available literature, I learned some geography: the Algarve and the Balearics have, magically, been added to the list in my head of Places I Want To Go.
Frommer's has a 500 Places to take the kids before they grow up (much like the places to go before you die) aspirational book. Not interested. Also, terrible reviews.
Judging by descriptions/reviews online, Lutz has the definitive get-out-of-the-house-with-baby/toddler book. And I think we probably zipped right past most of her recommendations, but I'll see if I can get it from the library just in case.
In any event, it looks like the field is good and growing. Further commentary on this subject will probably go into the parenting web over on my website, unless there's something juicily worth snarking about which might otherwise make me look bad over there, but which might be generally amusing over here.