One of the very best alternative emulators is probably Genymotion. This unfortunately is not free and is not as up-to-date as the native AVDs but it is fast and supports drag-and-drop file installation and mobile network functionality. It can be found at:
Another fast and easy to use emulator is Manymo. This is is a browser-based emulator and its primary purpose is to test web apps, but it works perfectly well for mobile apps. It too is not free but it does have a wide selection of ready-made form factors. It can be found at:
In a very similar vein there is Appetize, which is located at:
There are a growing number of such emulators but those mentioned above are probably the ...