Champions Online is now a free to play game. The game has been renamed Champions Online: Free-for-All and if you have a computer with an internet connection you’re good to go. Of course their are tiered membership levels in the “free-for-all”.
You can opt for a silver account, which will give you access to everything with just a few restricted bits of content. Or you can upgrade to a gold membership where you get access to more in game features like costumes and different adventures.
Personally I haven’t had the opportunity to check out the game yet, but it is definitely on my to do list. Head over to the Champions Online website for a free sign-up.