chain factor
A clever and highly addictive game, 'Chain Factor' is a kind of Four in a Row / matching tiles hybrid. It's also the first innovation in the whole 'Bejeweled' genre I've seen in a long time.
Apparently the game is part of a larger ARG related to an American TV show called 'Numb3rs', but it's very playable as a casual game as well.
See also this article by Jesper Juul on the history of matching tile games, including a family tree.