Conclusion
There are other websites that list popular baby names: BabyCenter, for instance, has a Top 10 Baby Names of 2004 list. However, their cited source is the Social Security Administration: they just repackage the data.
History of the Site
The original version of the Popular Baby Names site was the Report of Distribution of Surnames in the Social Security Number File, published "occasionally" [1]. GPO's Catalog of Government Publications lists only one of them:
Social Security Administration. Report of distribution of surnames in the social security number file, September 1, 1984. Social Security Administration, 1985. HE 3.2:So 1. Depository. CGP, accessed 3/28/2007.
In 1998, the SSA released Actuarial Note #139, Name Distributions in the Social Security Area, August 1997, which provides much of the same data that has subsequently been made available on their website.
Feature Request
While generally an excellent site, it is missing one key item: GET-style variables.

When you perform a search, the results page always has the same URL: http://ssa.gov/cgi-bin/babyname.cgi
Were GET-style variables to be used, the URL would be something like /babyname.cgi?name=Daniel&start=1984 – this would allow you to save searches and send them to others. Instead, this site cannot link directly to any searches it references.
References
- Actuarial Note #139, Name Distributions in the Social Security Area, August 1997: http://ssa.gov/OACT/NOTES/note139/original_note139.html

