A bit of conversation earlier about Rails set my brain onto a disastrous course. Since I've been doing so much with Ruby lately, it's only natural to have the question of whether anything can be done related to Rails hovering nearby at all times - Rails brought Ruby to prominence and is itself an amazing piece of software with a lot to teach. It's not, however, a natural fit for Domino - Rails, to my knowledge, wears its SQL proudly, and any attempt to use Domino as a backing data source would likely be more headaches than it's worth - you'd likely be better off either using Rails+SQL or XPages+Domino.
However, at least as far as my brain is concerned, that may not have to be the end of the story. Just because the data model doesn't fit doesn't mean that Domino-the-web-server can't be useful, right? Running Rails apps packaged as Websphere WARs is an actual thing you can do for some reason and, while Websphere seems to share more characteristics with a beast from Revelations than with a piece of software I'd want to install on my server, the concept is enticing.
Imagine: a Rails app stored in an NSF in the same kind of way you'd store Java classes or other Eclipse-y resources. It'd still use a SQL database as the back end, but it would "live" inside Domino. And, since it'd be inside an NSF and not some glorified ZIP file, you'd get replication, packaging, developer ACL control, and so forth (the sky's the limit if you mess with the views). Oh, not to mention NTF templates and access to the surrounding Domino environment as needed. It might actually be possible.
It might also not be possible. Off the top of my head, I can imagine that performance concerns, getting Rails to load its files from the NSF VFS, and handing off request routing to the Rails app all have the potential to be showstoppers. It's a nice thought, though, for down the line, after the more plausible things I'm working on are settled.