You might try installing matchbox; I believe that's what the maemo ui is built on. It works basically the same anyway (one app viewable at a time, not resizeable). If I remember correctly it's based on blackbox code and was originally intended for small handhelds. Quite workable, but I despise the one-at-a-time approach.
For me, lxde seems to be the best compromise between speed and features, but Icewm is even faster (it would be my second choice, and I may end up going back to it before long).