No need for a poll.
I have tested many of them. The two best ones in audio quality measurements:
1) Behringer UCA202 Audio Interfacehttp://www.amazon.com/Behringer-UCA202-Audio-Interface/dp/B000KW2YEI/ref=sr_1_sc_3?ie=UTF8&qid=1329582238&sr=8-3-spell
2) Griffin iMichttp://www.amazon.com/Griffin-Technology-iMic-Audio-Device/dp/B000BVV2IC/ref=pd_cp_e_0
That's not to say that others won't work well. I bought a large supply of the cheap $1 USB audio dongles from overseas and used them here and there. They seemed pretty susceptible to premature failure. So your mileage may vary with those. You get what you pay for. Also, they are better suited to mic level input rather than line level input. But they work in a pinch or on a budget...you have to control the audio level coming from the scanner very carefully or use an attenuating audio cable.
The main thing always is to pay very close attention to audio levels. The general goal is to keep the gain in the software mixer (in Windows or whatever OS you are running) as low as possible and use a volume setting coming from the scanner. This keeps hum to a minimum (unless you have a bad ground loop issue or power supply hum) - but either way the low input gain helps keep that noise to a very low level, under normal circumstances.