When my brother first visited Chicago after TJ was born, he brought a very thoughtful gift we had not seen before: The lila guide for San Francisco (where my brother lives). It was his way of saying, "Come visit, and bring the kid." And, we'll be taking him up on his offer shortly. We were just kind of hoping Elmo would come out with a 4-hour Lord-of-the-Rings-type epic in the interim to guarantee an uneventful flight.
Nonetheless, the lila guide was a great gift because it showed all the kid-friendly things we could do in San Francisco. While the lila guide ("Lila" is evidently the guide creator's daughter's name) started in San Francisco, there are now lila guides for 20 different cities in print, from Atlanta to Washington D.C. (They should do a Zephyr, Texas or Zion, Missouri guide just so they can get that whole "A-Z" gimmick working). Although a good chunk of each city guide pertains more to locals (sections on things like maternity stores, baby gear stores, mom's groups, etc.), each guide also covers essential info for traveling families: kid-friendly restaurants, parks, playspaces, and outings.
Although the books are handy to travel with and make a great gift, you can also get tons of relevant information from the lilaguide website for free. The site provides user-generated info for 26 specific locations (sorry, still no "Z" cities). So, if adding one more book to your packing list will break either your back or your budget, you can just check out the city you're visiting's lilaguide site before you travel. As an added bonus (warning: infomercial mode), if you contribute 10 reviews to the lilaguide website, you get a free hardcopy lila guide. It's a blogger's dream: getting paid to push your opinion on others.