TWM really had something with the "iconify" management technique - you could shepherd many more windows than are comfortable on most modern desktops, provided you were disciplined with placement. Nowadays I find myself grubbing around alt-tab entirely too much. Expose-like previewing looks sorta similar, but I don't find myself using it much because the layout is autogenerated, and it's hard to sift through your windows when they're tiny. I liked the spatial management.