Many people asked me this question - What is the best method to start learning Navision ? Actually, there is no specific right or wrong answer to this question. It's all depends on individual preference and the time and cost that you are willing to spend.
If you are looking for something free, you can always start with the Application Designer Guide and other pdf documents in the Navision installation CD. Unfortunately, the pdf documentation in the installation CD are more on technical area. If you have access to the partnersource or customersource, you can always download the training documentation for both technical and functional areas.
If you are willing to invest a small amount on book, then you can get the Programming Microsoft Dynamic Nav by David Studebaker and Managing Your Supply Chain Using Microsoft Navision by Scott Hamilton. You don't have much choice because there are only a few Navision books available in the market.
All the above methods required you to spend time to read the books or documentation. If you don't have the patience to sit down and read the book and prefer to attend class, you can always register for the instructor led class conducted by Microsoft's partner. It will be best if your company is willing to sponsor you on this because it is quite costly. Make sure you are able to free yourself from your job for about a week to attend the class.
If you don't have the patience to read the documentation by yourself and cannot afford to off work for a week to attend instructor led class, E-Learning is another option for you. ELearning allow you to control when you want watch the online presentation and is more cost efficient compared to instructor led class.
A few days back, I just got to know an ELearning portal, called SpeedTeach E-Learning Portal (http://www.speedteach.com/). SpeedTeach provides ETraining on both Navision Application and Navision Development. The courses are priced competitively from USD 75 to USD 499. I have tried the Financial module, the presentation is interesting and the sound quality is clear on my 1 Mbps internet line. I get a bit impatient on the waiting time when I tried it on the 512kbps line. Just my personal opinion, I think this course is more suitable for beginner learning Navision Financial module. SpeedTeach has 2 learning approach for you to choose - Conceptual Approach and Procedural Approach. Conceptual Approach is more theoritical oriented while Procedural Approach is practical oriented. You can choose conceptual approach, procedural approach or both of them. I personally prefer the procedural approach.
Again, to make it clear, I am not saying ELearning is the best option to learn Navision. I just listed out the options we have. It's all depends on individual preference. It is also not the more money you spend, the more you learned. Some people learned best by just reading the pdf documentation, which is the chepest option.