There are 2 ways to get the audio from those DATs into your Mac, an analog transfer and a digital transfer. A digital will sound better but will cost a bit more.
For analog, the other poster was correct, you can buy an analog 1/8" stereo to 1/8" stereo cable at the shack, plug one end into the DAT's line out or headphone out, and plug the other end of the cable into the mic's mic input port. This analog transfer method will go through a stage of digital to analog conversion and some slightly noisy circuitry on both the DAT and the Mac, and then through a stage of analog to digital conversion, all of which will degrade the sound quality somewhat. Maybe not enough to notice though.
Also, If using this method, be careful to pay attention to the input level you set on the Mac, if the level overloads you get digital distortion, which manifests as clicks and pops.
The other (and better) method is a digital transfer, which will preserve the audio quality perfectly since it's just transferring the digital bit from the DAT tapes, with no conversion, and no trip through analof circuits. Since your Sony portable has no stock digital I/O ports on it, you have a couple of options:
option 1-Find, on ebay or craigslist, a used DAT deck that has an optical digital output on it as a stock feature (all consumer models that are stereo component size will have one). Sometimes you can find these decks for just $30-50.
option 2-Buy the adapter cable to convert your Sony's 7-pin digital I/O port to a standard RCA connector (coaxial) digital output. You can buy one here
http://www.core-sound.com/7-pin-coax-blurb/9.php
for $45.
Then you will also need a coaxial digital audio to optical digital audio converter, to convert the adapter cable's RCA output to an otpical signal that can work with the optical input on your macbook.
Monoprice sells one here
http://www.monoprice.com/products/product.asp?c_id=104&cp_id=10423&cs_id=1042302&p_id=2947&seq=1&format=2
for about $11.
With these two adapters (and the appropriate optical cable), you would have what you need to get the sound into your mac with no extra conversions. You also won't have to worry about record levels, when doing a digital transfer there are no record levels to set.
From there it is as the other poster said, simply edit the clips in Audacity and then export to Mp3 files, ready to post to the website.
Thanks!
