Brendan Burns has created a GUI designer for Android called DroidDraw. The tool runs via an Applet, and allows you to select components and put them onto the canvas.

A tutorial gives you a full walk through of the tool and how it works:

This tutorial will give you a brief introduction to developing a GUI application on Android using the DroidDraw user interface designer. This tutorial assumes that you have downloaded and installed the Android SDK. This tutorial also assumes that you are reasonably familiar with concepts in GUI programming and the Java programming language.