Here is a list of links that you might find helpful and useful in your musical studies!
Low Brass Resources
Low Brass Organizations
St. Louis Low Brass Collective
International Trombone Association
Practice Tools
Online Metronome
Printable Manuscript Paper
Instruments
Care and Cleaning Tips (a great article by my friend and colleague, Lauren Husting)
The Brass Exchange (local shop for trying out and purchasing horns - primarily trombones)