yesterday, the international mozart foundation has launched a website called digital mozart edition, which apparently contains 95% off all musical compositions of wolfgang amadeus mozart.
there are more than 600 (preserved) compositions, or about 26.000 pages of sheet music, 24.000 of which are already online.
by 2009, they’re planning to have everything online (including digitalized lyrics and fulltext-search), and in 2010 they’ll start digitalizing the sheet music itself, making it possible, for example, to extract just the trumpet part of an entire symphony.
i think it’s even more impressive that they’re not trying to make money by selling subscriptions etc. instead, it’s all freely available to anybody.