The Birds Choice Fly-Thru bird feeder is a good pick if you want a feeder that is easy to put the feed in.
There are no sides on it and birds can literally fly through it if they want.  Of course that will also cause the squirrels to like it too I'm sure.  There is a mesh bottom in it so if the seeds do get wet they aren't going to mold and maybe the leftovers will fall through but I think it's more for ventilation because the holes are pretty small.
It comes with a small cable already installed to make it easy to hang in your favorite spot to watch the birds.  I used a metal shepherd's crook and it works perfect.  You can also move the roof out of the way if you need to so you can put the seeds in it or clean it.
The downside is it is made of plastic so I hope the squirrels don't decide they like the taste of it.