For random nerdery:
Behind the Name has probably the most accurate meanings/etymology of baby names on the internet.
Name Nerds has greats lists of "theme" names, and satisfies my love of Welsh & Scottish names. It also has incredibly helpful spelling-adjusted rankings for the US, and England & Wales as well.
Appellation Mountain has "profiles" on an ever-increasing variety of names, ranging from the everyday to the rare.
Nordic Names, as the name suggests, focuses on names used in Scandinavian (of any origin), and has many names & variants absent from other sources.
Forvo is a database of spoken word & names--great for actually hearing names from native speakers!
And of course, the SSA has yearly lists of the top 1000 since the 1879. That's a lot of names!
For help finding and testing baby names:
Behind the Name has a program to help you find the right name.
The Nymbler takes names you like, and produces a list of similarly-styled names.
Nameberry has an extensive database of names, including modern variants, as does
Baby Names World, which also has a nice user-friendly advanced search function.
The Baby Name Wizard takes the SSA data, and puts it into fun charts & maps.
For information about common "Native American" baby names misconceptions, check out Native Languages.http://www.native-languages.org/wrongnames.htm
You can create lists for others to rate at both Behind the Name (yes, again) and BabyNames.com.
I also hang out at the Baby Names forum on BabyCenter.
Other occasional sources:
The Catholic Encyclopedia
Dictionary of Names from Medieval Sources
Hitchcock's Bible Names Dictionary (PDF)
Irish Names, Donnchadh Ó Corráin & Fidelma Maguire
Key to English Place-Names
Kirchenweb German Name Lexicon (in German)
Lexicon of Greek Personal Names
The Viking Answer Lady