Lee Sin is one of my personal favorites when it comes to the jungle. His ability to counter-jungle as well as lane presence is almost incontestable. Lee Sin is a very mobile jungler and has a great ultimate to set up good ganks. The Blind Monk is also a very difficult jungler to master due to his ability set and skillshots. Although Lee Sin is a champion that takes practice, once learned, Lee Sin can change games.

Pros

Very Mobile
Counter-Jungling Beast
Strong Ganks
Counters a lot of other junglers
Very fun to play

Cons

Difficult to play
Not a lot of CC
Weaker ganks post level 6

9x Greater Mark of Attack Damage
9x Greater Seal of Armor
9x Greater Glyph of Magic Resist
3x Greater Quintessence of Attack Damage

The runes are very standard for Lee Sin jungle. I get the flat MR and the flat Armor because it helps more in the early game (ganks, jungle, etc.)

Essential summoner spells for Lee Sin jungle. Flash allows you to set up strong/needed ganks as well as escape near death.