using a 3.5mm or 1/8'' Male to 2 PHONO STEREO RCA Y CABLE ADAPTER http://www.a1netusa.com/images/SS-R62R1S.jpg to L/R input on cassette player. You might need a small preamp in between. Play your mp3 with WMP or other player on computer and record with cassette recorder.
Seen many postings on converting cassettes
to MP3, but not the otherway around.
Need to convert a bunch of MP3's to
cassette.
What software/hardware do I need?

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic