I have a years worth of Rachael Ray Magazines that I'd like to post on the Book Bazaar for a possible swap. Is it ok to do this or is it against the rules to post unpostable items?

I believe you can post them for FREE but, you can't ask for a credit.  I think but, I haven't looked at the HC for sure.

ETA:  I went and looked this up on the Book Bazaar Guidelines and here is what it said...

 (3) No selling books for anything but credits, and no offering anything but books for credits. Freebies/incentives can be "non-swappable" items, but remember that non-Media-Mail eligible items CANNOT be sent using Media Mail postal rate. For example, DVDs and VHS tapes and magazines and pamphlets/booklets without ISBNs are all NOT permitted to be posted at PBS; they can all be offered as freebies/incentives, though. But if the freebie/incentive items contain advertising (ie, magazines or booklets bought at a supermarket checkout stand), or are not Media items (anything but books, CDs, DVDs, VHS tapes) they can't be sent Media Mail, so the whole package will have to go by another shipping rate. DVDs/VHS tapes/CDs can be sent using Media Mail postal rate.

So, I guess it is like I first answered...you can offer them as a Freebie/incentive but, you can't swap them.  Also, note that you can't mail them Media Mail so, you might want to keep that in mind because I'd think a years worth of magazines could cost a bunch to mail.