I'm using AndEngine in my Android app. I found that this library is distributed under GNU Lesser GPL. What should I write in my about view to conform this license?
http://www.gnu.org already provides that information. Here's the link for that. In this link you may find a brief explanation of how to place a program under several licenses including GNU Lesser GPL.
EDIT: I checked some examples of LGPL'ed software in Ubuntu and their about boxes.
Licensing and Legal information
This product is made available subject to the terms of GNU Lesser General Public License Version 3. A copy of the LGPL license can be found below.
Jump to LGPL Version 3
Wine is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 2.1 of the License, or (at your option) any later version.