Here are some links to Relics Resources:
Relics - pious and by no means comprehensive (I mean....how can you write a book on relics and not mention the corpse of St. Catherine of Bologna on display, seated upright in a golden chair??)...but a useful start.
Furta Sacra about the theft of relics during the Central Middle Ages.
Magnificent Corpses is a guide to some saints' relics in Europe, but is of no use beyond that - the author is not a Catholic, which is fine - (I found the book on Marian shrines by a self-identified agnostic Virgin Trails quite a lovely and compassionate read) - but her description of her experiences of the relics, in every single chapter follows the exact same, numbingly dull pattern: Here's the relic. Here are the relic viewers who are either uncouth, obviously tourists rather than pilgrims and are often wearing obscene t-shirts. Well - so? There are many interesting points to be made about the intersection of pilgrimage and tourism, of the totality of experience and life that people bring to religious shrines - but the author doesn't try to make them.
There are some interesting and helpful sites on the web, in no particular order:
Two medievel critiques of the cult of relics:
And finally, the column I wrote that was the root of the talk