For a while there has been a number of Sonic CD hints, there was never a formal announcement. This lead to a lot of speculation of when the title would get announced. This however is no longer the case. Today gamers can buy Sonic CD on the Xbox or European PSN, but US gamers will need to wait a week. The game will sell for 400 MSP and will sell for $5.00/£3.59/€4.49 /AUD$6.25 on the PSN.
If you’re finding the wait hard, you can always import a European PSN card or download the awesome theme.