The promotion begins April 2nd, including the official M&M Star Wars web site, which provides more information on the bags and even a video segment of M&M Fett flying out of the Sarlacc.
To view the trailer: access the M&M site, click the Trailer link on the right, and chose your preferences. [Video no longer available.]
And, finally, a full checklist of every package in the line featuring Boba Fett:
#17/72: Dark Chocolate (3.14 oz)
#23/72: Dark Chocolate Peanut (3.27 oz)
#33/72: Dark Chocolate (14 oz)
#37/72: Dark Chocolate Peanut (14 oz)
#40/72: Dark Chocolate Peanut [Editor's Note: mislabeled on source] (14 oz) + #56/72 (21.3 oz)
Compiled by The Boba Fett Fan Club, for your collecting enjoyment, a web-ready checklist thanks to the source made available by M&Ms (below).
Boba Fett fans note: the coolest bags are the smallest size, #17 and #23, which are 100% Boba Fett.