Any voting system will require you to register. If it doesn't, it will be easy to manipulate. Trello doesn't allow me to make voting completely open. It's a bit ironic that you write your response in a forum you also needed to register for. ;-)
On the one hand I understand your concern, on the other I don't know how to do it differently.
I thought at least lots of people will already have a Trello account. And if they don't, I can at least whole-heartedly recommend it as it is an amazing tool I love and use every day. It is done by a company many people trust, Fog Creek Software, the company originally behind StackOverflow.com.
I could have done a Google spreadsheet, but then again, many people don't trust Google. I could have done a wiki page, but that would not be very user-friendly and is also too easy to manipulate. There are voting plugins for DokuWiki, but I would have only allowed logged-in users to vote, so people would have needed to register as well. I could have used SurveyMonkey, but that's too easy to manipulate either... The list goes on...
If you really don't want to register on Trello, you could tell us what you would vote for on the
according forum post and I will try to count those votes as well. But then again, your wiki users will need to *register* here, so, that might not help you much either.
You could also reply with votes to the mailinglist email, but that would also require you to register for that... I guess whatever solution I choose, it will be impossible to make everyone happy.