Here is a great article in Knitcircus with a free pattern to knit a hat and blanket. Preemies need little hats since such small babies lose body heat through their heads.
This article gives contact information for the NICU at Johns Hopkins in Baltimore for donations but you can also call your local hospital's volunteer services to see about a local need. Either way, consider knitting something for these little babies.
If you know of some other online resources for knitting or crocheting for NICU's or other charity crafting needs, please post in a comment. Thanks!
PS... Here is a link to LIONBRAND YARN'S Charity Connection