Not strictly HG-related but Tim Van Eyken presented an interesting programme on Radio 4 yesterday about the use of the internet and ABC to rediscover old tune books. It's still available on the BBC iPlayer and will be repeated at 15.30 on Saturday.
Chris Walshaw's new abc site (http://www.abcnotation.com
), mentioned in the programme, was experiencing a few glitches when I first tried it but it seems to be up and running now.
I really like the interface at http://www.folktunefinder.com
which also searches abc collections.