I would recommend a pair of sunglasses that have interchangeable lenses - that is to say smoke/red/yellow/clear or something like that. I bought a pair like this for about £15 sterling, and find the different lenses very useful in different lighting conditions; the clear or yellow being great for really dark days or at night. Or maybe you live somewhere that is always sunny, unlike me!
I see a pair like this with four lenses is available in the US for $20 from www.probikekit.co.uk
I have found them to be excellent at keeping the wind out of my eyes, and for this money it doesn't matter when I drop them under my wheels trying to put them on whilst cycling.