I posted this as a comment in another thread, but it probably qualifies for its own post.
Here is a link to a really nice replacement headphone jack at a great price.
If that link dies, search for a 3.5mm 8-pin (the important part) headphone jack. It should cost about $4.50 for 15 pieces. The replacement is really high quality and much sturdier than the flimsy original, but I had to sand a tiny bit out of the case to make it fit. I used a Dremel and then cleaned it with a rounded file.