Hi, Kat
Writer's Market carries a list of suggested rates for many different types of writing, you might check the 2001 edition to see if they cover the sort of contribution you have in mind.
(BTW - As of this year, I decided to subscribe to the on-line edition of WM; costs nary a whit more than the CD-included paperback and it's updated daily - so no more post-its festooning my dog-eared volumes as editors come and go and markets change or go out of business. A very good investment if you've not already come across it yourself!)
Good luck - and congrats.