The Kuznetsov trace formula on SL(3,Z) has yielded many number theoretic applications, such as results on the distribution of Maass forms and on symmetry types of families of L-functions. I will give an overview of this trace formula, focusing on the analysis of its geometric terms, and describe how one can obtain an orthogonality relation for the Fourier-Whittaker coefficients of a "thin" family of Maass forms.
Links:
[1] http://www.mpim-bonn.mpg.de/taxonomy/term/39
[2] http://www.mpim-bonn.mpg.de/node/3444
[3] http://www.mpim-bonn.mpg.de/node/246