small creep camps spawn at 1:40, and respawn after 1:20
Blue and red buffs spawn at 1:55 and respawn after 5 minutes
Dragon respawns after 6 minutes
Baron respawns after 7 minutes
To put this into context, if you're jungling and follow the standard route (blue buff, wolves, wraiths, red, golems) then your blue buff will respawn at around the 7:20 mark, and the red around 9 minute mark. This can come in very handy if you are counter-jungling. Also, if you are duo laning, the enemy jungler will be at the double golems just after you reach level 3 and will be low on health (having just killed the lizard), making them vulnerable to a gank.