This mount is sold by Fedryen Swiftspear, the Cenarion Expedition quartermaster, at the Cenarion Refuge in Zangarmarsh. It is rideable by players who have a riding skill of 300. Its cost is 2000 (1600 with the Exalted discount of 20%. 1400 with the Level 24 Guild Perk Bartering.).
Wrath of the Lich King
In WotLK, as of patch 3.2, two other hippogryph mounts exist, the Silver Covenant Hippogryph and Argent Hippogryph. Each is available from vendors for 150 after completing certain quest and reputation requirements, however the Silver Covenant Hippogryph is only available to the Alliance.
In patch 3.3, animations for standing on the ground, walking, and running were added to all hippogryph mounts. Prior to this patch, hippogryphs would simply hover at ground level (with a speed reduction as with all flying mounts), much like nether rays.