There are a large number of 40-80Msample/sec ADCs that are used for digitizing video signals. The current set of high end ADC's runs in the Gsamples/sec range and are used for radio and specialized sensor applications. Look for parts from Analog Devices, Maxim, TI, National, (and probably any other company which makes analog parts). Finding a fast ADC isn't difficult - dealing with the 40-1000MB/sec data output is.
Fer example, the Analog Devices, AD9200 is a 10 bit 20MS/s ADC. There looks like there are higher speed variants - which go up to 100MS/s.
So here's a question back: what are you connecting the ADC to?