Some important ones are, like vWii channel forwarders (such as USBLoader GX), SDCafiine is, the Plugin System is, and I think the vWii overclock app (always forget it's proper name) is too.
.elf is outdated and restricted compared to .rpx though, that's part of what this move is all about it seems. In order to push the limits of what can be done in these environments, it appears that it will be important for .elf to be left behind. My understanding is that Aroma straight up wont load .elf homebrew at all. At least that's what I last heard a few months back from Maschell himself.