Behringer UCA202 USB Interface:
http://www.samedaymusic.com/product--BEHUCA202
RCA in/out, optical out, monitors/headphone out, volume control for monitors.
for $35 shipped.
vs.
Griffin iMic2 USB Audio Interface:
http://www.buy.com/retail/product.asp?sku=202151596&SearchEngine=PriceGrabber&SearchTerm=202151596&Type=PE&Category=Comp&Gad=0&dcaid=15890
in/out 3.5mm stereo mic/line, toggle switch for mic/line setting.
for $31 shipped
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problem with the Behringer one, is that I'd have to carry an extra RCA->3.5mm adaptor, if I'm going to be carrying that around. But optical out would be awesome. And volume control for the monitor out? I guess.. it'd be more useful for at home, tape->CD conversion things...