First off, if you haven't seen the old skyblock map... you're missing out on a lot of context. But the short version is: I made a lot of rails. Check out this overviewer-powered render of the map here (download and extract the large zip file, and then open index.html, allowing scripts if prompted - it's an interactive render). The skyblock map is also (still) up for download on mediafire (you will need 7-zip or another extractor to open this RAR file); there's access to the nether if you fly behind the windmill (~100 blocks).
I really enjoyed handling this transportation for the community, and I'd like to do something like this again. But, right now the islands are fairly close, so there's no real reason to make it in the nether. Instead, it should be done in the overworld.
Basically,