THADDEUS

also known as Judas, son of James, and or Lebbaeus

Mark 3:16-19
 These are the twelve he appointed: Simon (to whom he gave the name Peter); James son of Zebedee and his brother John (to them he gave the name Boanerges, which means Sons of Thunder);  Andrew, Philip, Bartholomew, Matthew, Thomas, James son of Alphaeus, Thaddaeus, Simon the Zealot and Judas Iscariot, who betrayed him. 
NIVJohn 14:22
  Then Judas (not Judas Iscariot) said, "But, Lord, why do you intend to show yourself to us and not to the world?" 
NIV
Acts 1:13
  When they arrived, they went upstairs to the room where they were staying. Those present were Peter, John, James and Andrew; Philip and Thomas, Bartholomew and Matthew; James son of Alphaeus and Simon the Zealot, and Judas son of James.
NIV
Luke 6:16
 Judas son of James, and Judas Iscariot, who became a traitor. 
NIV

REFERENCES

THADDAE'US (tha-di'us). A name in Mark's catalog of the twelve apostles (Mark 3:18) in the great majority of manuscripts. From a comparison with the catalog of Luke (Luke 6:16; Acts 1:13) it seems scarcely possible to doubt that the names of Judas and Thaddaeus were borne by one and the same person. Edersheim (life of Jesus, 1:522) derives the term Thaddaeus from thodah, praise. KJV (Matt 10:3) lists him as "Lebbaeus, whose surname was Thaddaeus."
(from The New Unger's Bible Dictionary. Originally published by Moody Press of Chicago, Illinois. Copyright (c) 1988.)

HISTORICAL ACCOUNTS
 

Thaddaeus is reported to be one of the first apostles to go a foreign country in his ministry. His ministry  carried him to Syria, Armenia and Persia.  Bartholomew and Thomas appeared to have joined him for a period of time. He was martyred and was buried near the Caspian Sea in what is now modern day Iran.