http://certsphere.com has free practice exams. You can take test #341 (the multi-platform exam version), or #340 (the basic websphere exam).
The site also gives you the option to receive explanations, and links to actual IBM material about each question. I believe this information is normally available for $25, but right now it is being offered for $10. [ October 27, 2004: Message edited by: Phill Evens ]