my own inclination would be to go with some tab-top sheers or light cotton panels on a single rod across the top of the windows (put the rod a few inches above the frame if possible). Prices vary on these dramatically, but if you sew, even a little, you could actually whip up something quite decent using bedsheets, of all things. Yes, bedsheets.
Where else can you get a huge piece of material like that for a reasonable price?
a twin flat sheet makes a great panel and it's dead easy to cut a few inches off the bottom to create the tabs, or leave it as is (i.e already hemmed) and just pick up a couple of pillowcases to use for tabs. Tabs can be as simple as a doubled strip of cloth, neatly stiched and hemmed, and sewn to the back of the sheet. There's enough fullness to hide the stitching from the outside when the drapes are pulled back.
Of course, now someone's gonna ask if I've taken my own advice and done that in my own new house - nope, we're still surviving on the ugly drapes that were in the house, supplemented by heavy paper accordian blinds that were only about $5 ea at Home Depot. They look really good from the outside, and not too bad from the inside (if you can ignore the big spring clips that are used to hold them open and the fact that they're "peel and stick" at the top. Sounds a lot worse than it looks, and is just the ticket in this place with its surfeit of narrow, hard to fit windows.
Once I get the supplies and the time, I'm going to be making roman blinds for the living room front windows and we're going to paint the high small side window with "Gallery Glass" paint to simulate a stained glass window (the husbandperson is quite artistic).