Here's a tutorial on machine by Kevin Knight. This is gives excellent, accessible coverage and we'll go through this in class to get a grasp of how MT works.
Knight1999StatMt_wkbk.rtf
Here are some other references that cover specific techniques or comparisons.
BrownDelaPietra1993_J93-2003.pdf
AlignCompare-J03-1002.pdf
HMMWordAlign-p836-vogel.pdf