A very good source of resources and information for players at any level, mainly trombone specific information but the breathing and home practice articles are brilliant and there are further links at the bottom to learning more advanced skills like double tonguing

A collection of free links to a large number of resources for all types of brass playing

Free Downloadable resources including fingering charts slide position charts and warm up guides from one of the largest musical instrument makers in america

Large wealth of information on the Tenor Horn, photos on how to hold it, mouthpiece and mute information as well as history, very enlightening

Techniques and advice on developing a good full dynamic range, no blastissimo on the loud bits

This list will be updated as and when new sources of information are found, please feel free to comment if there are any resources you're unable to find or if you've found something that could be of use to others