A nice post in The National Archives blog on Documenting LGBT history across the UK - which is as much about bringing things into visibility within existing archives as generating new sources such as oral history. A bit miffed that they don't mention the Wellcome!
Not archives, but rare books: Kerala State Central Library: Rare Books Online. These look like very much the kind of things that are very difficult to find.
Though, while I'm delighted the researcher found it: Found: 500-year old wanted man warrant for Machiavelli, the Florence State Archives are pretty much the place that one would start looking, surely ! How lost was this item, or was it just a case of going through files and files of unindexed early C16th warrants?