Dvolver movie maker is really a good resource. You can write as many scenes as you want, a maximum of 6 lines per scene and you can include quite long texts. No log in and you can send it to anyone.Great recommendation!
Create your avatar with Hero Factory: http://cpbherofactory.com/. It is quick and easy but you can not save or send it.
Professor Garfield is an amazing tool to create comic strips very quickly. It is ideal for beginners that do not how to write long texts.
Symbaloo is a multiple resource website similar to pinterest but more varied in topics and resouces because it gives direct connection to webpages.