TYLER - In 2 Nephi 25:29 it tells us to worship Jesus Christ with all our might, mind and strength etc. If you don't believe in the trinity (where Jesus would therefore BE God) How can you justify worshiping both God the Father and Jesus Christ? wouldn't that be in direct violation of the commandment quoted by Jesus himself, "thou shalt worship the Lord thy God, and him only shalt thou serve." it seems to me that regaurdless of whether you believe other gods exist you are only allowed to worship ONE God and only one. (and a polytheistic view of the Godhead would be included, you cannot worship the father and the son if they are not the same God.)
Also, why does Thomas say to Jesus, "My Lord and my GOD" John 20:28. It appears as though Thomas believed in the trinity, (and John as well since it is him who is writing it).

JOEL - The Father and the Son are the same God, even though we believe they are separate individuals. We worship only one God, and that one God is God the Father, Jesus Christ, and the Holy Ghost. They are separate and distinct beings and are individually called "Gods"(plural), but the three of them together are also called "God"(singular). The word "God" can represent one being or all three beings; it depends on the context in which the word is used.
We believe that scriptures that tell us to worship only one God are refering to the Godhead, consisting of the three. We do not worship Gods of other universes in the past or present; only the God of this universe. It's kind of like a basketball team. People in Utah are fans of the basketball team called "Jazz"(well most are). They are fans of each team member who is a "Jazz" and they are fans of the team as a whole which is also called "Jazz".

When Thomas felt with his own hands the risen Christ, he was just expressing his testimony that Jesus is Lord and God. Jesus can be called Lord and/or God and God the Father can be called Lord and/or God. They are just different names used for identifying a member of the Godhead. I don't see how this scripture is proof of the concept of the trinity. It's all in how you personally interpret it.
The words "Lord" and "God" are a little different in that "Lord" can refer to one who is a master over many and "God" refering to an all-powerful, all-knowing, supreme devine being. So Thomas is professing his realization and belief that Jesus is both his master and his devine being(God). But God the Father can be called both of these things as well.
See also the following page:
http://www.mormonhaven.com/tomjohn2.htm