The use of interactive web technologies on public library web sites in the United States has been a topic of much discussion in recent years, and a shift in certain types of user services is underway. Terms like "Web 2.0" and even "Library 2.0" have become common in library literature and at conferences as those on the early edges of this shift share their successes and failures with the broader library community. The Library Research Service (LRS) was interested in adding to this conversation and, in late 2007, designed the study U.S. Public Libraries and the Use of Web Technologies. In spring 2008, LRS staff visited the web sites of nearly 600 public libraries in the United States, searching for the existence of certain web technologies, including technologies defined as "Web 2.0." The web sites that were examined were drawn from a stratified sample of public libraries in the United States, with approximately equal numbers of libraries included from each of five different population ranges. Additionally, staff visited the web sites of all public libraries in Colorado. Two main sets of results were derived from the study: (1) how many public libraries in the United States (and Colorado) were implementing certain technologies on their web sites, and (2) what were the characteristics of the libraries that could be identified as "early adopters" of web technologies. A third set of conclusions -- does the early adoption of such technologies increase the libraries success in traditional service areas -- awaits the release of more current, available national public library data. Library 2.0 survey is appended. (Contains 6 tables, 20 charts, and 4 footnotes.) [This report was produced by the Library Research Service (LRS), a unit of the Colorado State Library, Colorado Department of Education Education, that is operated in partnership with the Library and Information Science Program, Morgridge College of Education, University of Denver.]