If you're giving someone an iPhone for Christmas or Hanukkah, you must also give that person a copy of iPhone Fully Loaded, 2nd Edition, by Chicago Sun Times columnist and MacBreak Weekly co-host Andy Ihnatko. I read the first edition when it came out, and the chapter on iTunes smart filters alone improved my experience with the iPhone.
The other chapters are also very useful. You'll learn the easiest way to get DVDs, internet videos, VHS tapes, broadcast TV episodes, podcasts, e-books, comics, songs from various sources, Office documents, and lots of other kinds of media onto an iPhone. You'll learn how to turn text files into audiobooks, and watch videos hosted on an online dropbox.
Even if you didn't have an iPhone, you could pick up a lot of useful computer and media tips here. As a bonus, Ihnatko's wry sense of humor makes the book a lot of fun to read.