- Head over to http://developer.android.com/sdk/eclipse-adt.html#notes and pick which pick which version you want to use again.
- Create your download url: http://dl.google.com/android/ADT-##.#.#.zip. Google uses the version number for the downloads, so if you need 15.0.1, your download would be http://dl.google.com/android/ADT-15.0.1.zip.
- Install the new version as an archive (Help --> Install New Software ---> Add --> Archive)
This should get you back to developing!