Taunt
Taunt is useful to keep mobs focused on tanks instead of damage dealers and makes it easier for the healers.
Note: taunt is not rage!
When a tank with 50 taunt deals 100 damage, mobs will think that tank did 150 damage. When there is also a damage dealer that does 140 damage, the mob will attack the tank.
Skills
Tank skills that provide lots of taunt are Shield, Cow, Staff.
Other Skills that provide taunt are Deer, Warden, Ice Magic, Animal Handling, Unarmed, Psychology, Lycanthropy, Necromancy.
Some damage dealer skills with taunt are Archery, Fire Magic (pet), Spirit Fox (pet), Battle Chemistry (pet).
Some skills also give reduced taunt for those that do not want to pull aggro.
Other sources
Taunt can also come from generic equipment mods, words of power, alcohol buffs.