In one folder, we are using Tasks as individual subject items for in-house training seminars and we'd like to allow our users to vote on the next subject (task) to discuss.
Have you thought about using the "multiple assignees" option for the voting?
Anytime someone wants to vote they could assign themselves to that task, and whomever would be running the seminar could be added via a custom "people" field, or have the actual event added as a subtask or checklist item assigned to them.
You wouldn't be able to tally the votes though, so hm....
You could also create a numbered custom field labeled "votes" and anyone voting could simply update the number by one increment. Then you could easily sort it by number of votes.
It's not as fun as the fancy little triangles we get to click here to vote, but it might make an ok workaround in the meantime.