What is the ruling on trusts in my possession? Must they be returned to their owners or must they be informed of them, knowing that they are few and have been held for a long time, or is it permissible to give them away in charity?

Any items found whose owners are known must be returned to them, and there is no harm in contacting them. As for items whose owners are unknown, they fall under the ruling of a "Luqatah" (found property). It is permissible for the finder to utilize items of negligible value, which the owner would not typically pursue. It is also permissible to give the value of such items in charity on behalf of their owners.