A great, long-term solution: go through closet (and dresser) and just donate all the old clothes I don't wear anymore.
The easy solution: something apparently everyone else already does, but I couldn't resist sharing for the three of us still out of the loop. I present, double-hanging!!
This works especially well with tank tops or dresses on hangers with these hook-things (yes, that's the technical term for them).
Added bonus: by mixing up what shirts you hang together, you can even stumble across new outfit inspirations, like I did with my favorite chambray shirt and a yellow oxford sweater that I never wear.