Warm-Ups
Horn Maintenance Video - BBC Symphony Orchestra principal Nick Korth demonstrates shows some warm-up tips in the second half of this BBC video tutorial (for the first half of it shows basic horn maintenance tips).
The Importance of Warm-Ups - article by Jean-Pierre Mathez, editor of The Brass Bulletin
Daily Routine - thoughts on the subject by Frank Lloyd
Warm-up exercises (whole body, not with instrument) for performers - pdf download. With diagrams.
Tuning
Tuning the Farkas Double Horn - by Philip Farkas. One of the many excellent articles on the Osmun web site.
Tuning the Double Horn - John Ericson's explanation of tuning the double horn.
Guidelines for Tuning the Horn - by Curtis Hammond of Morehead State University; pdf file.
Tuning the Horn - Selmer-Conn
Tuning the Horn - Hornstuff
Intonation Procedure for Tuning a Double Horn - article by Eldon Matlick
Understanding Brass Instrument Intonation - ditto
Tuning (3) - from the archives of hornplayer.net
Tuning the Double Horn in Just Intonation - pdf file
Tuning a Horn with No Bb Slide - courtesy of Stuart DeHaro
Intonation: Bane and Grail - article by Stephen Colley, developer of The TuneUp System
Tuning the Standard Double Horn - by Simon Locke
Embouchure
40 Embouchures from Farkas's Photographic Study of Embouchures - a list of the players
Embouchure 101 - article by John Ericson
Embouchure Health & Maintenance - article by Andrew Pelletier
The Balanced Embouchure - by Jeff Smiley, a trumpet player & teacher, written for trumpet players, but intriguing for horn players as well. See the YouTube video demonstration.
Embouchure - Wikipedia article
Embouchure - The chapter on Embouchure from Wendell Rider's book, Real World Horn Playing. Also available in pdf form.
Embouchures.com - a primary resource for brass players with embouchure problems; excellent reference books for sale, including Broken Embouchures and Rehabilitating Embouchures.
Lip Vibration in Trombone Embouchures - It's not especially pretty, and it's not horn, but it's brass playing and it's fascinating. This link is a slow motion shot of embouchure lip motion through a clear mouthpiece. Among other things, it answers the question: do lips touch as they vibrate while producing a tone? There are many such videos available on this site.
Transposition
Horn transposition chart - Part 1 of 5 of the series "French horn transposition" by Bruce Hembd on the Horn Matters blog.
Transposing - Blog entry by Jonathan West in his Horn Thoughts. Interesting chart listing how many movements in the symphonies of Beethoven, Brahms, Dvorak, Mendelssohn, and Schumann are in which transposition, e.g. Horn in F: 72 movements; Horn in Eb: 40 movements; Horn in B natural: 4 movements.
Prelude to the 3rd Act of Lohengrin - "Study in transposition" - pdf file of the original orchestral part, courtesy of Bruce Hembd
Fingering Charts
Fingering Chart by Ron Boerger
Horn Harmonics - a moveable "wheel" chart that quickly & easily shows alternate fingerings for the double horn. See John Ericson's review.
Fingering Chart - courtesy Yamaha
Fingering Chart - from Conn
Fingering Chart for single F, single Bb & double horn - by John Ericson (pdf file)