You might try feeding hummingbirds. It's easy to do. The feeders are inexpensive, and you can make the nectar easily: Mix one part white table sugar in four parts tap water. Store in refrigerator until ready for use.
A few additional notes:
Nectar should be changed at least once a week, twice a week in hot weather. If it is allowed to stay out too long it can begin to ferment, which is bad for the birds.
Mold growth on the feeders can be prevented by running them in the dishwasher when you change the nectar. Many feeders, although mostly plastic, have metal parts, so it's best to put them on the top rack.
There's no need to get a large feeder. Ruby throated hummingbirds, the kind you're most likely to see in the Eastern US, don't play well with others. I've never seen more than one ruby throat on a feeder at a time.
If you can, use a feeder that has a perching rail. Although hummingbirds can and do hover, it helps them conserve energy if they can perch while feeding.
Adding an "ant well" (a small container filled with water) above the feeder prevents ants and other insects from getting in the feeder and spoiling the nectar.
You can hang the feeder as close to the window as you like. I have mine hanging from a suction cup hook on the window. Hummingbirds have no fear of people at all. I've had them land on the feeder while I was holding it preparatory to hanging it up.
