Nora Roberts' website contains a complete list of the books she has written over the years. The website is Noraroberts.com, and the list, which can be sorted from newest to oldest or by title, is the second option under the section heading called "The Library."
Nora Roberts has written books as J.D. Robb. These titles, all part of the "In Death" Series, are also listed under "The Library." In addition, the same list can be found by following the link to J.D. Robb's website, which is provided on the Nora Roberts' website under "The Author."
Finally, the website lists which titles are available as e-books or in audio.