Here's an ambitious new Mozart website that launched recently. It's called MozartWays. Eventually they hope to have the complete correspondence of the Mozart family, complete with links, footnotes, translations in multiple languages and much else. They already have maps of Mozart's travels through Europe; you can download a map, drill down to specific cities, find out about the Mozart sites in each, along with dates of his stay, anecdotes.....and that's the beta version.
This is the coolest site ever. Really brings the 'concert tour' of the 1700s to the present day.