I have accomplished this by recording through standard 1/8" mini-stereo plug into computer's sound card (line input) and using shareware (free) recording software Goldwave, available at goldwave.com. Just take the RCA's from your tapedeck or receiver/amp and buy a $3 radio shack plug from 2 RCA females to 1 stereo mini male.
What I did was record an entire side of the tape, then use Goldwave to split it into separate files for the songs, saving them as separate .wav files. Then burn with Easy CD Creator or Nero (which can also be used free for a month or two).
It will definitely not sound perfect, but it's free and you may be surprised at how good it sounds. I would definitely recommend trying this first and then spending extra money only if the sound is not good enough.