There are a lot of descent bird feeder plans out there, but I think this is simpler and better than most I've seen.
-Empty PET bottle (I recommend using one with a big mouth, as it will be easier to fill)
-Old plate or bowl
-Silicone glue (More flexible and deals better with temperature swings then standard glues)
a) Make a hole at the top of the bottle top. Make it big enough to be able to fit the shoe lace through it.
b) Pull shoe lace through hole, and through washer, then tie a double knot.
a) Cut 3 or 4 evenly spaced hole very close to the bottom of the bottle. Don't make them too big (you could always make them bigger later on, if not enough feed comes through).
b) Drill a few small holes (3-4mm) in the plate to allow for water drainage.
b) Clean the surfaces to be glued.
c) Apply 5 or so gobs of silicone glue to the bottom of the bottle, and center it on the plate.
d) Apply pressure and let dry for 24 hrs.
a) Fill up bottle (use funnel if you need to).
b) Hang outside.
c) Refill as the birds finish the food.