I have found a couple of places to practice our craft:
CBS and Mock Draft Central.
CBS is totally free and you can do as many as you like. MDC is free, if you want to do one a day, but pay-per for more.
Try both:
http://mockdraft.1.baseball.cbssports.com/mockdraft/standard?ttag=fbbmd10_on_all_cspt_fbn_mb_0001
http://www.mockdraftcentral.com/index.jsp
