Recently I got a native Chinese language tutor and I am following something like an official program as taught in the Chinese language university classes around the world. The tutor confirmed the books I recommended before are very good and that she knows personally the author to be a very good teacher.
I also enjoy the free KT-Dict CE application for IPod/IPhone realised by Klaus Thul
that also have a very good page on why and how to learn Chinese language at http://www.klausthul.com.
As you may already know, IPod Touch is a great tool to exercise writing in Chinese,
still the paper and the pen are the fundamental tools.
Will be back on this subject.