The message broker server that backs the feed system is currently non-responsive, and I'm waiting on the server host to perform an actual, physical intervention.
I'm not sure when things will be fixed, but things may be down for a day or two.
Ok, normal feeds should be resuming now. The issue should be resolved.
For the technically inclined, the problems resulted from the combination of a bug in RabbitMQ (the message brokeer the feeds use), and an issue with the linux tool mountall. The RabbitMQ issue (specifically the fact that the "Shovel" plugin caused it to get stuck on exiting) caused me to simply decide to reboot the server. The issue with mountall then caused the server to not start up properly after reboot (it was stuck waiting for a partition that doesn't exist to mount).
I've removed the shovel plugin entirely, and added a work-around to fstab to prevent the reboot blocker issue, and it shouldn't reoccur.