I found this site the other day, and I definitely want to share this one with IAB.
The game is a free download, you create an account at first launch, it doesn't even ask for an email (you can stay offline if you choose). Just login online, click 'Play,' then find yourself a level to start with. You can sort by Most Popular or I highly recommend searching for Yoku-Tetris level... it's a blast.
On top of it all, you can create your own levels using sprites from the first 5 Mega Man games. All the logic is included as well for enemy behavior.
I have no idea how they are not getting a cease and desist order from Capcom yet, but I for one am enjoying the hell out of it until they do.