Several great references are available on CD to assist with VAM identification:
8TF Attribution Wizard: This is the first of a series of Attribution Wizard software developed by John Baumgart and Jeff Oxman. It has done the unthinkable and made attributing 8TF Morgan Dollars easy. This CD contains over 600 pictures of all 41 8TF varieties (currently doesn't include clashed dies). The Attribution Wizard presents you with a pictoral flowchart of what to look for on your coin and presents you with an attribution when it is known. In addition, you can browse through varieties or individual dies. The 8TF Attribution Wizard also has a trainer to quiz you on the varieties -- which is a great study aid for bourse floor preparation. The software also includes current values which can be downloaded over the internet when they are updated.
79S Rev. of '78 Attribution Wizard (2005): All 17 varieties of 79S Rev. of 78, same features as 8TF Wizard.
Hot 50 Attribution Wizard (2003): All Hot 50 varieties, including those for which multiple varieties count for a single Hot 50 coin. No trainer, since it is not an exhaustive date/mint list like the 8TF or 79S Rev. of 78.
Top 100 Attribution Wizard (2006): All Top 100 varieties, including those added through 2006, same features as Hot 50 Wizard.
Top 50 Peace Dollar Attribution Wizard (2007): All Top 50 Peace dollars, with features the same as the Hot 50 and Top 100, but also including die progression studies of the 13 major die break Top 50 coins.
7TF Attribution Wizard (2008): This has the same features as the 8TF Wizard, but covers all 7/8 TF and 7TF B-reverse coins (VAMs 30-198).
New: Hit List 40 Attribution Wizard (2009): All Hit List 40 varieties including important die progressions. Same features as Hot 50 and Top 100 Attribution Wizards.
The price is $24.95 each plus shipping. They're available directly from John Baumgart ([]) as well as other venues.