A recent post from The Rock n Coder covers the advantages of using Oracle's virtual machine app, VirtualBox, as an Android Emulator. There are some disadvantages to simply using a device to debug, and an alternative to Google's emulator is definitely welcome. The post offers step-by-step instructions on setting up the Android virtual machine in VirtualBox, as well as a few quick tips, like using cloned VMs, to save you some trouble down the line. Aside from lack of support from Google, the VirtualBox emulator looks solid.
I remember loading the Android emulator in Eclipse for the first time and staring blankly as it loaded for about fifteen minutes, so it's great to see a faster alternative. There are better things to do, after all, than watch things load. Check out the full post if you're interested in an Android emulator that moves a little (or a lot) faster.