Training on Specific Flavors
As you no doubt already know, there are many different types of Linux. If you have already chosen your Linux distribution, then you will need to find the training for your specific flavor. Here are links to training for some of the most common varieties.
This is the official documentation for the Red Hat operating system. This site will give you all of the training options, from self study to in-person sessions that you can schedule with a trainer. You can also find forums on this site which can help you get answers to specific questions that you may have.
This site uses what is known as "Knowledge Base" to help you to find what you need. You can search for information using key terms. If you don't find what you want, just hover over "Help Yourself" to get access to the forums and the documentation for the operating system.
Sometimes the best help is other people. These forums include a wide range of topics that have already covered, and you can ask your own questions if you don't find what you need.
It is worth noting that if you have a less documented version of Linux, or one that is not as popular, that you will most likely not find any formal training out there. If you need help, what you should do is go to the forums associated with the distribution. The odds are that you will find most of your questions answered already. If not, people in the Linux forums are usually more than happy to help.