Gleemax.com is a website associated with Wizards of the Coast, publishers of Axis and Allies, D&D, and now Heroscape.
They are in the alpha phase of online play, which includes free online Axis and Allies. It is java based, so it runs on damn near everything, including Linux. And since it has the look and feel of the real A&A, it gives TripleA a run for its money, even though it is still in pre-release, with some features missing.
I'm not sure if this will cost money to play in the future, if it will continue to be free, or if they will have a 'get some time free with purchase, and pay more later' model, like Days of Wonder's Ticket to Ride.
Lets hope they also figure out some way to do this for Heroscape as well.