Not entirely related to Ars Magica, and I'm sorry if it's impolite to post about another company's products in Atlas' forums, but Green Ronin is having a sale on the Medieval Player's Manual, a book about playing medieval with D&D rules written by a certain David Chart. It's offered for only 10$, and it's part of a sale they are having to raise funds to pay their freelancers (so supposedly David will see most of the money you spend on this?).
I just thought it might interest some of the crowd. Specifically,
I have long had a copy of this - it's interesting to compare Atlas Game' own Occult Lore, Ars Magica's "The Mysteries" (4th Ed) - both with substantial contributions by Adam Bank - and The Medieval Player's Manual. TMPM is a strong book, and has material of interest to the ArM player though you have to modify the underlying rules.
It does have rules for Book Fights! (Debating battles fueled by scholarly quotations!)
As for the Freelancer's Sale - there is a sorry tale at http://www.greenronin.com/index.php?id=P416#news_top wherein Green Ronin explain that their past distributor stole substantial amounts of revenue - GR are now stable again and paying off debts, but in an effort to bring forward payments to their freelancers, they're having a special sale, and even asking specifically for donations to the freelancer's fund.
Without this, they say they will pay the freelancers eventually but it's slow, and they feel the freelancers particularly deserve a better deal.