Ikea's ideas for maximizing small spaces are pure genius. In this video, the part featuring the walk-through closet starts at 2:52.
photo credit: www.ikea.com
Here's another idea from Ikea: the use of a curtain behind the bed's headboard to serve as a partition for the dressing area.
This led me to further research on walk-in closet alternatives. While Ikea's curtain partition seems to be much easier to execute, I'm partial to having a wall, which can be the back of one of the closet shelves.
photo credit: Clayton Hauck for Builder
Such would work perfectly for small, narrow bedrooms.
photo credit: www.shelterness.com
With more space and a horizontal bedroom layout, these pegs can work as well.