Many times I have built home-brew radio to computer sound card audio interfaces with success. The goals were to have some fun with the many digital modes out there including PSK31, MFSK, Olivia and RTTY with an emphasis on PSK31.
Also available for use are handy CW decoders like CWGet and CWSkimmer.
To complete the computer to radio marriage I purchased and built a WinKey and Winkey USB kit from K1EL.
By this time, the number of cables between the computer and the radio was getting a little out of hand. I sought a new approach that connected to the computer with just one cable.