There are several jungling tips/guides for Summoners Rift (SR - standard 5v5 map). Is it possible to jungle in 3v3 and what would be the differences to SR? If so how and which heroes are good for jungling on TT?
Jungling 3v3 is possible and is seen in higher ELO games. There are lots of videos showing it on own3Dtv. I recommend browsing Twisted Treeline videos to see how it's done.
Good junglers for 5v5 also are good junglers for 3v3, but keep the differences between 3s and 5s in mind. In addition to aggressive dps champs being favored in 3v3, there is more competition for the small number of camps in the jungle. Aggressive junglers do well because they have plenty of opportunities to harass the enemy; Nunu and Cho Gath come to mind, both being strong junglers with good ganking potential and great harassment. If you watch some Twisted Treeline games you will see non-aggressive junglers like Warwick being dominated.