The dragon in Summoner's Rift spawns in an alcove in the middle of the lower river between the middle and bottom lanes. It spawns at 2:30, and it has a respawn time of 6:00.
Killing dragon gives each champion on your team 190g, with a 25g bonus for whoever landed the final hit. This is roughly worth 6 entire creep waves, making him a high-value target. He is also worth 400 total experience, though the experience is not global.
His attacks add a damage over time effect, as well as a 20% attack speed reduction debuff. He is also immune to crowd control effects, as well as armor and magic resistance shred effects. Furthermore his damage can't be decreased.
He has 3030 + (220 * highest champion level) HP, 190 AD, 21 armor, and 30 magic resist.
These stats are summarized, and they do repeat some information that is shown above.
Gold: 190 (Global) (+25 to killer)
Experience: 400 (Global)
Health: 3030 (+220 * highest champion's level)
Attack Damage: 190
Magic Resist: 30
Critical Strike Chance: 0%
Attack Speed: 0.658/sec
Movement Speed: 330
Initial Spawn Time: 2:30
Respawn Time: 6:00