Ive found stuff like this:
http://www.amazon.com/Logitech-3-5mm-Jack-Audio-Adapter/dp/B0058P0I2C/ref=cm_cr_pr_pb_t
and this:
http://www.amazon.com/GTMax-Female-Microphone-Adapter-Lanyard/dp/B0032AEF42/ref=sr_1_5?s=electronics&ie=UTF8&qid=1352148509&sr=1-5&keywords=usb+to+3.5mm
but have no idea how much I need to spend to get decent sound.
Also, my computer thinks there is something plugged in and won't let me switch the output to the onboard speakers... can I change this?
BTW I have a 15" MBP from early 2011.
Thanks for any help!