There is a lot of examples of various types of finite p-graups having abelian automorphism group. In 1913, the first example a non-abelian group of order 64 such that Aut(G) is an elementary abelian group of order 128 has been constructed by G.A. Miller. A comprehensive survey about such groups can be found in: Vivek K. Jain, Pradeep K. Rai, and Manoj K. Yadav's preprint in arXiv: 1304.1974v1 [math. GR] 7 Apr 2013.