I'm not sure whether there is an online resource listing banding/tagging programs so that people can contact them regarding sightings, but we can create one here. Just post comments here with contact details and I'll put them in a list.

I see Jon has created a Bands observed field, so I have added that as an option when adding observations to this project.

You can go back and add that field to observations already added to the project. No strict format, but for birds generally note colours and metal bands, left leg first, in a format like "metal/yellow, red/white/dark green"

(click on the journal's title (above) to see the discussion/comments section for this project)