When I'm in the early stages of planning (and writing) a book, names are important. They help me to set my characters and once they're set, they tend to be set in stone. That's part of the reason prospective parents spend so much time on choosing their baby's name. It's a major commitment.
But whether you're a writer trying to name a character or a prospective parent trying to come up with something new or clever (or traditional), it helps to have a resource. And while there are plenty of baby name books that will do the job, and I own and use many of them, Name Voyager is a favorite website, because it offers something that books don't. You plug in a name and it instantly graphs the name, showing you the popularity arc from the 1880's through the present (or at least as far as statistics are available).
It's fun and sometimes I find myself trying out different names just to see the historical pattern of each name. If you want to give it a try, the website is babynamewizard.com.