I suppose that you can use the Tuple
class (http://msdn.microsoft.com/en-us/library/system.tuple.aspx), like this:
var ChannelQueue = new BlockingCollection<Tuple<ChannelResource, String>>();
ChannelResource ChanResource = TelephonyServer.GetChannel();
MyApplication.ChannelQueue.TryAdd(Tuple.Create(ChanResource, "someString"));