NewEgg has a lot of SSDs. If you're just looking at read speeds and price, then the OCZ Vertex series are a good value: http://www.newegg.com/Product/Produc...82E16820227393 $149
I have the 120GB version in my laptop, it works great and is very fast. OCZ has a new firmware update and a "TRIM" utility (shouldn't be needed for a carpc, but it helps keep the drive at top performance) for the Vertex series.
I spent a lot of time years ago working with CF and other flash devices for carpcs, but honestly I don't see the need or advantage nowadays. SSDs provide better performance and usability and none of the compatibility headaches of CF, USB, or other flash devices.