To access the thousands of templates open up your Google Apps and select Create > From Templates. You can narrow down what you are looking for by the type of document or by the category it might fall in to. You can also try searching the template section for something you are specifically looking for. Once you find what you need you can Preview it and select Use This Template which will place the document in your files.
There is another saying that "It is better to give than to receive.", and so the option is there for you to submit a template as well. Simply create the document in your own files and then when you are ready to share it, you navigate to the template gallery and select Submit a Template found in the top right hand corner. Fill out the required information and viola!