I recently found this untagged tag. It now contains 134 questions on Stack Overflow. (If you can't vote to delete, you can focus on the open questions.)
(Update: now - 2011-07-12 13:53 UTC - 106 ones are left, of which 53 are non-closed.)
As one can't create untagged questions (and I doubt anyone puts this tag intentionally on his question), these most likely occur either through migration from other sites (see the migrated questions tool), by expiring seldom-used tags (e.g. these which are used only once, and created more than 6 months ago), or by burninating tags that are not wanted (often after a request here on meta).
Either way, I found that the list of these questions seems to be a good list of questions which could be worked on:
- quite some are simply off topic (example), and should be closed and/or migrated (but possible tagged first to get them off the list).
- others are on-topic, but need some editing, and/or only proper tags.
This is not so much a question, but more a call for volunteers: If you have some superfluous time, go through this list and tag/flag/close-vote these questions. (Or answer them, after tagging.)
Of course, proper tags here means normally tags which are already used for other questions, else we have the same problem again after some months.
UPDATE as of today (2nd October) there are still 37 untagged questions. I've [ChrisF] been through them and they're all pretty much off topic so I've cast votes as appropriate. I've also cast delete votes on the ones that are already closed.
Update as of now (UTC 2011-10-03 11:22) there are zero untagged questions. I've [AakashM] been through them and votes close / delete as possible, and retagged them all (even the closed ones, because hey, I'm a programmer, and there are either zero or not-zero such questions in the system :)
untagged
one is the most obvious. You already know every question with that tag needs cleaning up before you even go into it.