Some time ago I was playing with a new method of semi-auto-discovery of OAI-PMH endpoints. I've not done any work on it in a while so I decided to throw it up on github.
The thing most likely to be of interest is a list of endpoint's baseurls. There are 43808 of them, which seems a lot compared to other lists I've seen. There's some duplication (http / https / IP URLs that clearly point to the same content) but it seems to have relatively good coverage of OJS installs, particularly those outside of the English-speaking world.
cheers
stuart