They are still very desirable CDs. The ones that haven't been opened should sell for a premium price -- especially if they are ones that are not now available and someone really wanted it. Check the prices on ebay.....
The Martha Pullen CDs are also especially nice and are very pricey if you buy them new.
As far as different brands of embroidery machines using these CDs, most CDs will have a list on the back of what programs that are available on that particular CD: art. is Bernina, etc.
Let us know if you'd like to sell or trade some of them.... :D