The Samaritan Passover has just been celebrated (April 28, 2010). In so doing, they mainly follow the instructions of Exodus 12 and Deuteronomy 16 in sacrificing lambs, albeit with a few local traditions as well. This is performed on Mount Gerizim together with the eating of the lambs in the same night. Any left overs are burned before daybreak.
Aren Maeir, a professor at Bar Ilan University was invited to the latest event and blogs about it--including photos--on his blog. It is worth a read as it captures some of the atmosphere that must have pervaded the temple in Jerusalem during prior to C.E. 80.
Interestingly, the Passover is kept at the beginning of the 14th according to the Hebrew Calendar, but in this case on the second month. Whether this was an intercalary year for the Samaritans is not given. I've tried to find information previously on the Samaritan calendar but have not found anything of substance on-line.